Topiramate

Rodrigo Martino, M.D., Ph.D.

• Attending Senior Physician
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• Hospital de la Santa Creu i Sant Pau
• Barcelona, Catalonia, Spain

Maternal Causes of Growth Restriction Maternal health conditions associated with chronic decreases in uteroplacental blood flow (maternal vascular diseases medicine 6469 topiramate 100 mg buy otc, preeclampsia symptoms dizziness nausea topiramate 100 mg buy low cost, hypertension medications used for fibromyalgia topiramate 100 mg purchase without prescription, maternal smoking) are associated with poor fetal growth and nutrition medicine names purchase topiramate 100 mg on-line. Preeclampsia has been shown to be associated with fetal growth restriction (Ødegård et al 7mm kidney stone treatment order topiramate 200 mg on-line, 2000; Spinillo et al, 1994; Xiong et al, 1999). Investigators have shown that the extent of growth restriction correlates with the severity and the onset during pregnancy of the preeclampsia. Chronic maternal diseases (cardiac, renal) may decrease the normal uteroplacental blood flow to the fetus and thus may also be associated with poor fetal growth (Spinillo et al, 1994). Maternal weight (pre-pregnancy), maternal stature, and maternal weight gain during pregnancy are directly associated with maternal nutrition and correlate with fetal growth (Clausson et al, 1998; Doctor et al, 2001; Goldenberg et al, 1997; Mongelli and Gardosi, 2000). Numerous studies show that these findings are often confounded by highly associated cultural and socioeconomic factors. A large population-based study in Sweden found that women who were older than 30 years, were nulliparous, or had hypertensive disease were at increased risk of preterm and term growth-restricted infants. It is unclear whether these differences in fetal growth are caused by inherent differences or by differential exposure to environmental factors. Maternal nutrition and supply of nutrients to the fetus affect fetal growth significantly, primarily in developing countries (Doctor et al, 2001; Godfrey et al, 1996; Neggers et al, 1997; Robinson et al, 2000; Zeitlin et al, 2001). Furthermore, pre-pregnancy weight may be a potential marker for intergenerational effects on infant weight in developing countries. Teen pregnancy represents a special condition in which fetal weight is highly influenced by maternal nutrition. Teen mothers (younger than 15 years) have been shown to have a higher risk for delivering a growth-restricted infant (Ghidini, 1996). Teen pregnancies are complicated by the additional nutritional needs of a pregnant mother, who is still actively growing, as well as by socioeconomic status of pregnant teens in developed countries (Scholl and Hediger, 1995). Maternal nutrition and maternal weight gain are adversely affected by inadequate or poorly balanced intake in conditions such as alcoholism, drug abuse, and poverty. The effects of micronutrients on pregnancy outcomes and fetal growth have been less well studied. Maternal intake of certain micronutrients has also been found to affect fetal growth. Zinc deficiency has been associated with fetal growth restriction and other abnormalities, such as infertility and spontaneous abortion (Jameson, 1993; Shah and Sachdev, 2001). In addition, dietary intake of vitamin C during early pregnancy has been shown to be associated with an increase in birthweight (Mathews et al, 1999). Others have shown strong associations between maternal intake of folate and iron and infant and placental weights (Godfrey et al, 1996). In developing countries, the effects of nutritional deficiencies during pregnancy are more prevalent and easier to detect. Rao et al (2001) have estimated that one third of infants in India are born weighing less than 2500 g, mainly because of maternal malnutrition. These investigators have shown significant associations between infant birthweight and maternal intake of milk, leafy greens, fruits, and folate during pregnancy. Although toxins such as cigarette smoke and alcohol have a direct effect on placental function, they may also affect fetal growth through an associated compromise in maternal nutrition. Numerous studies have shown associations between birthweight and maternal intake of macronutrients and micronutrients, but the effects of nutritional supplements used during pregnancy on fetal growth are equivocal (de Onis et al, 1998; Jackson and Robinson, 2001; Rush, 2001; Say et al, 2003). This finding is underscored by the results of a recent, large, double-blind, randomized controlled trial including 1426 pregnancies in rural Burkina Faso (Roberfroid et al, 2008). Numerous investigators have shown a significant effect of socioeconomic status on birth outcomes, including fetal growth restriction, in both developing and developed countries (Wilcox et al, 1995). In the United States, low levels of maternal and paternal education, certain maternal and paternal occupations, and low family income are associated with lower birthweights in children of African American and white women (Parker et al, 1994). In a large population-based study in Sweden, investigators have shown a higher incidence of fetal growth restriction in association with low maternal education (Clausson et al, 1998). Researchers have also shown that rates of compromised birth outcome are higher among African American women than among Mexican American and non-Hispanic white women (Collins and Butler, 1997; Frisbie et al, 1997; Thomas et al, 2000). Other researchers have shown that Mexican-born immigrants in California have better perinatal outcomes (including birthweight) than African Americans and U. The reasons for this apparent paradox are unclear, but one postulate is the tendency of recent immigrants to maintain the favorable nutritional and behavioral characteristics of their country of origin (Guendelman and English, 1995). These studies support the speculation that the differences in fetal growth between groups do not reflect inherent differences in fetal growth, but rather stem from inequalities in nutrition, health care, and other environmental factors (Keirse, 2000; Kramer et al, 2000). Smoking Cigarette smoking is consistently found to adversely affect intrauterine growth in all studies in which this factor is considered. In developed countries, cigarette smoking is the single most important cause of poor fetal growth (Kramer et al, 2000). Cigarette smoking has a significant effect on abdominal circumference and fetal weight, but not on head circumference (Bernstein et al, 2000). Other researchers have shown that even a reduction in smoking is associated with improved fetal growth (Li et al, 1993; Walsh et al, 2001). Numerous potential causes of the effects of smoking on fetal growth have been suggested, including direct effects of nicotine on placental vasoconstriction, decreased uterine blood flow, higher levels of fetal carboxyhemoglobin, fetal hypoxia, adverse maternal nutritional intake, and altered maternal and placental metabolism (Andres and Day, 2000; Pastrakuljic et al, 1999). Data also suggest that the more severe the growth restriction, the worse the neonatal outcomes, including risk of stillbirth, fetal distress, neonatal hypoglycemia, hypocalcemia, polycythemia, low Apgar scores, and mortality (Kramer et al, 1990; Spinillo et al, 1995). The effects of acute fetal hypoxia may be superimposed on chronic fetal hypoxia, and placental insufficiency may be an important etiologic factor in these outcomes. The incidence of adverse perinatal effects correlates with the severity of the growth restriction, the highest rates of respiratory distress syndrome, metabolic abnormalities, and sepsis being found in the most severely growth-restricted infants (Spinillo et al, 1995). Preterm infants with growth abnormalities have a much higher risk of adverse outcomes. Neonatal hypoglycemia and hypothermia occur more frequently in growth-restricted infants (Doctor et al, 2001). These metabolic abnormalities presumably occur from decreased glycogen stores, inadequate lipid stores, and impaired gluconeogenesis in the growth-restricted neonate. Developmental Outcomes: Early Childhood Neurologic outcomes, including intellectual and neurologic function, are affected by growth restriction. The rate of cerebral palsy is also higher in preterm growth-restricted infants than in preterm infants with appropriate fetal growth (Gray et al, 2001). Other researchers have shown higher rates of learning deficits, lower intelligence quotient scores, and increased behavioral problems in children with a history of fetal growth restriction, even at 9 to 11 years of age (Low et al, 1992). The term programming describes the mechanisms whereby a stimulus or insult at a critical period of development has lasting or lifelong effects. The "thrifty phenotype" hypothesis proposes that the fetus adapts to an adverse intrauterine milieu by optimizing the use of a reduced nutrient supply to ensure survival; but because this adaptation favors the development of certain organs over that of others, it leads to persistent alterations in the growth and function of developing tissues (Hales and Barker, 1992). In addition, although the adaptations may aid in survival of the fetus, they become a liability in situations of nutritional abundance. In their study, the prevalence of diabetes in subjects 20 to 39 years old was 30% for those weighing less than 2500 g at birth, 17% for those weighing 2500 to 4499 g, and 32% for those weighing 4500 g or more. The risk of developing type 2 diabetes was nearly fourfold higher for those whose birthweight was less than 2500 g. The highest risk for the development of type 2 diabetes is among adults who were born small and become overweight during childhood (Eriksson et al, 2000). Similar findings were reported in 10-year-old children in the United Kingdom (Whincup et al, 1997). In a Finnish cohort, adult hypertension was associated with both lower birthweight and accelerated growth in the first 7 years of life. In contrast, in two preliminary studies from the United Kingdom, catch-up growth in the first 6 months of life was not clearly related to blood pressure in young adulthood, although birthweight was (McCarthy et al, 2001). Interpreting the findings of these studies is complicated by the vague definitions of catch-up growth. This definition allows for fetal growth retardation at any birthweight; large fetuses can be growth retarded in relation to their genetic potential. However, postnatal factors can obviously affect infant growth in the first few months of life. For example, breastfeeding appears to protect against obesity later in childhood, but breastfed infants usually exhibit higher body mass during the first year of life than formula-fed infants. Although it is likely that accelerated growth confers an additional risk to the growth-retarded fetus, these conflicting results demonstrate the need for additional, carefully designed studies to determine how childhood growth rates affect the later development of cardiovascular disease and type 2 diabetes. Epidemiology It has been recognized for nearly 70 years that the early environment in which a child grows and develops can have long-term effects on subsequent health and survival (Kermack, 1934). The landmark cohort study of 300,000 men by Ravelli et al (1976) showed that men who were exposed in utero to the effects of the Dutch famine of 1944 and 1945 during the first half of gestation had significantly higher obesity rates at the age of 19 years. Men who were smallest at birth (2500 g) were nearly sevenfold more likely to have impaired glucose tolerance or type 2 diabetes than those who were largest at birth. Barker et al (1993) also found a similar relationship between lower birthweight and higher systolic blood pressure and triglyceride levels. Valdez et al (1994) observed a similar association between birthweight and subsequent glucose intolerance, hypertension, and hyperlipidemia in a study of young adult Mexican American and non-Hispanic white men and women participants in the San Antonio Heart Study. Normotensive individuals without diabetes whose birthweights were in the lowest tertile had significantly higher rates of insulin resistance, obesity, and hypertension than subjects whose birthweights were normal. Growth-retarded fetuses and newborns have been shown to have a reduced population of pancreatic cells (Van Assche et al, 1977). However, none of these earlier studies adjusted for the corresponding insulin sensitivity, which has a profound effect on insulin secretion. Jensen et al (2002) measured insulin secretion and insulin sensitivity in a wellmatched population of 19-year-old, glucose-tolerant white men whose birthweights were either less than the 10th percentile. To eliminate the major confounding factors, such as "diabetes genes," the researchers ensured that none of the participants had a family history of diabetes, hypertension, or ischemic heart disease. When data were controlled for insulin sensitivity, insulin secretion was found to be lower by 30%. Because of the retrospective nature of the cohort identification, many confounding variables were not always recorded, such as lifestyle, socioeconomic status, education, maternal age, parental build, birth order, obstetric complications, smoking, and maternal health. Instead, birth anthropometric measures were used as proxies for presumed undernutrition in pregnancy. Some of these determinants may be related to susceptibility to adult disease, and others may not. Conversely, some prenatal determinants of adult outcomes may not be related to fetal growth. A good example of how size at birth may potentially be a proxy for an underlying causal pathway is the hypothesis that essential hypertension in the adult is caused by a congenital nephron deficit (Brenner and Chertow, 1993). This study shows that kidney volume is smaller in adults who were thinner at birth, after adjustment for current body size. In contrast, maternal cigarette smoking is a good example of a prenatal exposure that restricts fetal growth, but to date no association has been found between cigarette smoking and adverse long-term outcome in offspring. Genetics versus Environment Several epidemiologic and metabolic studies of twins and first-degree relatives of patients with type 2 diabetes have demonstrated an important genetic component of diabetes (Vaag et al, 1995). In other words, the genotype responsible for type 2 diabetes may itself restrict fetal growth. This possibility forms the basis for the fetal insulin hypothesis, which suggests that genetically determined insulin resistance could result in insulin-mediated low growth rate in utero as well as insulin resistance in childhood and adulthood (Hattersley et al, 1999). Maternal gene expression can alter the fetal environment, and the maternal intrauterine environment also affects fetal gene expression. An adverse intrauterine milieu is likely to have profound long-term effects on the developing organism that might not be reflected in birthweight. Cellular Mechanisms Fetal malnutrition has two main causes: poor maternal nutrition and placental insufficiency. In the extensive literature about the fetal origins hypothesis, these two concepts have not been discerned clearly. Such a distinction is necessary, because maternal nutrition has probably been adequate in the majority of populations in which the hypothesis has been tested. Only extreme maternal undernutrition, such as occurred in the Dutch famine, reduces the birthweight to an extent that could be expected to raise the risk of adult disease (Lumey et al, 1995). The oxygen and nutrients that support fetal growth and development rely on the entire nutrient supply line, beginning with maternal consumption and body size, but extending to uterine perfusion, placental function, and fetal metabolism. Interruptions of the supply line at any point could result in programming of the fetus for the future risk of adult diseases. The intrauterine environment influences development of the fetus by modifying gene expression in both pluripotential cells and terminally differentiated, poorly replicating cells. The long-range effects on the offspring (into adulthood) are determined by which cells are undergoing differentiation, proliferation, or functional maturation at the time of the disturbance in maternal fuel economy. Slowed growth in late gestation leads to disproportionate organ size, because the organs and tissues that are growing rapidly at the time are affected the most. For example, placental insufficiency in late gestation can lead to reduced growth of the kidney, which is developing rapidly at that time. Reduced replication of kidney cells can permanently reduce cell numbers, because there seems to be no capacity for renal cell division to catch up after birth. Substrate availability has profound effects on fetal hormones and on the hormonal and metabolic interactions among the fetus, placenta, and mother. Higher maternal concentrations of glucose and amino acids stimulate the fetal pancreas to secrete exaggerated amounts of insulin and stimulate the fetal liver to produce higher levels of insulin-like growth factors. Fetal hyperinsulinism stimulates the growth of adipose tissue and other insulin-responsive tissues in the fetus, often leading to macrosomia. However, many offspring of mothers with diabetes with fetal hyperinsulinism are not overgrown by usual standards, and many with later obesity and glucose intolerance were not macrosomic at birth (Pettitt et al, 1987; Silverman et al, 1995). These observations suggest that birthweight is not a good indication of intrauterine nutrition. Maternal factors associated with macrosomia during pregnancy include increasing parity, higher maternal age, and maternal height. In addition, the previous delivery of an infant with macrosomia, prolonged pregnancy, maternal glucose intolerance, high pre-pregnancy weight or obesity, and large pregnancy weight gain have all been found to raise the risk of delivering an infant with macrosomia (Mocanu et al, 2000). Maternal complications of macrosomia include morbidities related to labor and delivery.

For infants born prematurely or without organism-specific maternal IgG medicine ball discount topiramate amex, alternative or lectin pathway activation provides a critical mechanism for triggering complement effector functions (Maruvada et al medications 1040 order topiramate 200 mg on-line, 2008; Super et al treatment emergent adverse event topiramate 100 mg otc, 1989; Swierzko et al medicine qid purchase 200 mg topiramate with mastercard, 2009) medications via endotracheal tube purchase 100 mg topiramate fast delivery. For example, Stossel et al (1973) demonstrated opsonic deficiency in 6 of 40 cord sera examined because of decreased factor B concentrations, despite normal C3 and IgG levels. The functional contribution of the classic pathway to neonatal effector functions has been assessed through the use of cord blood­mediated opsonophagocytosis by adult polymorphonuclear leukocytes of group B streptococci type Ia (Edwards et al, 1983). This serotype may be opsonized by classical pathway components in the absence of specific antibodies and thus permits evaluation of the function of classical pathway activation. In 8 of 20 neonatal sera examined, decreased bactericidal activity was detected and correlated with significantly lower functional activity of C1q and C4. These studies did not determine whether this decrease was mediated by an inhibitor of function or by an intrinsic change in functional activity of these components in neonatal sera. The importance of the terminal complement component C9 for cytolysis of multiple isolates of E. Although lower serum concentrations of classical, alternative, and lectin pathway complement proteins can contribute to enhanced susceptibility of infants to systemic infection, other complement functions important for fetal and neonatal well-being, but not related to antimicrobial response, can contribute to reduced capacity to activate the classical and alternative pathways. For example, reduced serum concentration of C4b-binding protein (8% to 35% of pooled adult plasma levels), which is a critical regulator of classical pathway C3 convertase activity, has been noted in fetal and neonatal sera (Fernandez et al, 1989; Malm et al, 1988; Melissari et al, 1988; Moalic et al, 1988). Lower C4b-binding protein concentration increases the functional anticoagulant activity of protein S, with which it complexes and thereby contributes to decreased coagulation function of the fetus and newborn. Consideration of functions besides immunologic effector functions may be important in furthering the current understanding of the developmental regulation of complement component production. Concern has also been raised that unregulated complement activation can occur in selected infants who undergo extracorporeal membrane oxygenation therapy (Johnson, 1994; Kozik and Tweddell, 2006). Complement activation is an important regulator of multiple functions of the host immunologic response. Further study of the fetus and newborn infant will be aimed at understanding the developmental and genetic regulation of immunologic and nonimmunologic functions of this important group of plasma and cell surface proteins. Familial hemophagocytic lymphohistiocytosis arises from mutations in genes that encode proteins involved in the granule-exocytosis pathway and is a fatal disorder without bone marrow transplantation (Jordan and Filipovich, 2008; Orange, 2006). A third inhibitory receptor gene locus has been identified on chromosome 12p12-p13. Although this approach has been successful in some cases, the results have not been uniformly beneficial (Cairo, 1987; Cairo et al, 1984; Menitove and Abrams, 1987; Stegagno et al, 1985). This heterogeneity emphasizes the importance of individualizing immunologic interventions for the developmental stage of the infant and the invading microorganism being treated. The severity of functional differences correlates with the maturity of the infant and begins to decrease within the first few weeks after birth (Carr, 2000). For example, an activation product of the fifth component of complement, C5a, is a chemoattractant at sites of inflammation. Low concentrations of C5 in neonatal sera might not permit establishment of chemoattractant gradients at sites of inflammation in newborns comparable to those in adults. The recognition that systemic bacterial infection in newborns is frequently accompanied by profound neutropenia prompted the investigation of neutrophil kinetics in infected infants (Christensen et al, 1980, 1982; Santos, 1980). These studies have suggested diverse, developmentally specific regulatory mechanisms required for mobilization of the neutrophil response to infection. Unlike granulocytes, whose tissue half-life is hours to days, macrophages migrate into tissues and reside for weeks to months. In a tissue-specific fashion, these cells regulate availability of multiple factors, including proteases, antiproteases, prostaglandins, growth factors, reactive oxygen intermediates, and a considerable repertoire of cytokines. The importance of macrophages in the neonatal response to infectious agents has been documented in multiple studies. For example, increased antibody response and protection from lethal doses of Listeria monocytogenes were induced in newborn mice by administration of adult macrophages (Lu et al, 1979). This observation emphasizes the fact that fetal­neonatal monocytes­macrophages can have functions developmentally distinct from those of adult cells. For example, in utero production of growth factors and removal of senescent cells during tissue remodeling may be critical to fetal development (Kannourakis et al, 1988). Concurrent induction of these functions and immunologic effector functions in fetal monocyte­macrophages would potentially elicit nonspecific inflammation in actively remodeling tissues. Besides having antibacterial functions, neonatal monocyte­macrophages contribute to tissue-specific regulation of the microenvironment in individual organs. Because of the importance in tissue injury and repair, tissue and injury-specific treatment by appropriately targeted and primed monocyte­macrophages may provide therapeutic options for treating a spectrum of problems, from oxygen toxicity in the lung to hemorrhage in the brain. Some early T cell progenitors retain myeloid potential, suggesting a revision of the classic model base on the presence of a common lymphoid progenitor (Bell and Bhandoola, 2008; Wada et al, 2008). The process of lymphocyte differentiation is best viewed as a progressive narrowing of differentiation potential based on the sequential expression of specific transcriptional regulators (Mansson et al, 2010). T Lymphocytes T lymphocytes or T cells develop in the thymus, which is formed from the third branchial cleft and the third or fourth brachial pouch. Thymic lobes are generated when tissue from these sites moves caudally to fuse in the midline. Each lobe can be divided into three regions based on structure and function: the cortex, the corticomedullary junction, and the medulla. Maturation continues as cells migrate back through the cortex toward the corticomedullary junction. Weak interactions generate survival signals and continued development of positive selection. For many positively selected cells, subsequent high-avidity interactions with bone marrow­derived antigen-presenting cells in the thymic medulla result in activation-induced apoptosis or negative selection (Gong et al, 2001). For a small subset of thymocytes, high-affinity interactions with an agonist ligand can also induce a transcription factor, Foxp3, that is associated with regulatory T cell development rather than cell death (Jordan et al, 2001; Relland et al, 2009). In the human embryo, the first naive, mature T cells appear at approximately 11 to 12 weeks of embryonic development. Thymopoiesis continues for many years thereafter, and integrity of this process is essential for a healthy immune system. Thymectomy early in life results in a substantial loss of naive T cells and in an oligoclonal memory T cell compartment (Prelog et al, 2009; Sauce et al, 2009). The final phase of T cell development is independent of the thymus and involves peripheral (lymph nodes, spleen- and gut-associated lymphoid tissue) homeostatic mechanisms. These poorly understood events control the expansion of clones recognizing specific antigens and the development of T cell memory. Peripheral repertoire selection begins with migration of lymphocytes from the blood into lymphatic tissue. Lymphocyte attachment, coupled with the shear forces produced by blood flow, results in rolling of the lymphocytes along the endothelial cell surface. After entering the lymph nodes, movement of lymphocytes is also controlled by chemokines and their receptors (Worbs et al, 2007). After activation, changes in chemokine receptor expression control the mobilization and function of lymphocytes within the lymph nodes. T cell activation requires a complex molecular cascade that results in reorganization of signaling molecules in the membrane into an "immunological synapse" and in signal transduction (Bromley et al, 2001). The chain is thought to be the most critical component and is found as a homodimer. Appropriate phosphorylation of results in a downstream cascade that involves the tyrosine phosphorylation of multiple cellular substrates including phospholipase C1, the guanine nucleotide exchange factor Vav, and the adaptor protein Shc. Ultimately the genetic program of the cells is altered, leading to the transcription of genes for cytokines, cytokine receptors, and transcription factors (Cantrell, 2002). The cytokine milieu in the local environment during antigen presentation is a primary factor influencing the developmental fate of a naive T cell following activation. Th1 cytokines act synergistically to lyse virally infected cells and activate antigen-presenting cells as well as granulocytes. Human neonatal T cells are biased against Th1 polarization relative to adult T cells (Levy, 2007). Poor Th1 function is associated with impaired killing of intracellular pathogens and a reduction in vaccine responsiveness (Levy, 2007). Thus, Th2 cells are thought to promote antibody production and the allergic response by multiple mechanisms (Ouyang et al, 2001). Human fetal T cells are biased toward Th2 polarization (Prescott et al, 1998), and their abundant representation in the neonate contributes to the Th2 skewing of neonatal responses (Adkins et al, 2004). Abnormalities in Th17 cell development and function are also linked to immunodeficiency and autoimmunity. A maturational delay in the development of costimulatory function that contributes to reduced T cell responses in the neonatal period has been suggested (Orlikowsky et al, 2003), and the expression of costimulatory molecules is further suppressed by treatment with dexamethasone (Orlikowsky et al, 2005). These mechanisms reset the peripheral immune system and thereby maintain adequate clonal diversity. A small number of activated T cells survives, and these cells differentiate into memory cells (Wakim and Bevan, 2010). Late memory cells can become L-selectinhigh, which is a surface marker seen in naive T cells. The ultimate number of memory cells has been shown in mice to reflect the initial antigenic load and clonal burst size. Memory T cells allow the secondary response to be more rapid and more potent, characteristics that form the basis for vaccinations. In one study, preterm and term infants developed comparable memory T cell responses after vaccination (Klein et al, 2010). Maturation of immune responses continues throughout the first year of life, a fact that affects vaccination schedules (Gans et al, 1998). A low level of thymopoiesis has been shown to continue into adulthood (Kennedy et al, 2001). Regulatory T Cells Natural regulatory T cells develop as a distinct lineage in the thymus dedicated to maintaining self tolerance (Sakaguchi et al, 2008). Expression of the forkhead-winged helix transcription factor Foxp3 ultimately identifies these cell types and is essential for the acquisition of suppressive effector function (Zheng and Rudensky, 2007). Treg cells are required for the maintenance of immunologic tolerance, as illustrated by the autoimmunity that arises after neonatal thymectomy and by the fatal autoimmune lymphoproliferative disease that develops shortly after birth in mice and humans deficient in Foxp3 (Bennett et al, 2001; Brunkow et al, 2001; Chatila et al, 2000; Sakaguchi et al, 1995; Wildin et al, 2001). Treg cells have risen to the forefront of research in immunology because of their essential role in maintaining immunologic tolerance. Preclinical animal models have demonstrated that adoptive transfer of Treg cells can prevent or cure diabetes, experimental allergic encephalomyelitis (multiple sclerosis), inflammatory bowel disease, lupus, arthritis, and graft-versus-host disease (Hori et al, 2002; Kohm et al, 2002; Morgan et al, 2005; Mottet et al, 2003; Scalapino et al, 2006; Tang et al, 2004; Tarbell et al, 2004; Taylor et al, 2002). In humans, removal of Treg cells in vitro enhances the proliferation of T cells in response to self-antigens (Danke et al, 2004). Defects in Treg cell function and number have been described in a number of different human autoimmune diseases, including diabetes, multiple sclerosis, rheumatoid arthritis, and juvenile idiopathic arthritis (Baecher-Allan and Hafler, 2006). Clinical trials using the adoptive transfer of Treg cells after allogenic hematopoietic stem cell transplantation as therapy for graftversus-host disease have begun in Germany and are planned in the United States (Roncarolo and Battaglia, 2007). B Lymphocytes B cells are lymphocytes that upon activation give rise to terminally differentiated, immunoglobulin-secreting plasma cells. Immunoglobulins form the humoral arm of the immune system and provide the main form of protection against many pathogens. The embryonic phase begins in the fetal liver at the same gestational age as T cell development, follows a similar time course, and uses similar developmental strategies. Those progenitors with self-reactive receptors are either eliminated or generate new antigen receptors by continued gene segment rearrangements that are not self-reactive. Although the B cell compartment is well formed before birth, diversification of the antibody repertoire and several important antibody responses are not developed until long after the neonatal period (Hardy and Hayakawa, 2001; Rohrer et al, 2000; Rolink et al, 2001; Yankee and Clark, 2000). The early phase of B cell development, like T cell development, is antigen independent. Late cells in this stage express an invariant surrogate light chain (Kitamura et al, 1992). Cells with a nonfunctional H chain rearrangement or with H chains that assemble poorly with surrogate light chain are unable to progress. A second developmental checkpoint occurs here, and those B cells with self-reactive receptors are eliminated or edited (Hartley et al, 1991). Only 10% to 20% of the immature B cells survive this negative selection and migrate to the spleen, which they enter through the terminal branches of the central arterioles. Once in the spleen, they rapidly differentiate into mIgM+, mIgD+, B220+ mature B cells that enter the recirculating pool of B lymphocytes (Hardy and Hayakawa, 2001). Immunoglobulins Immunoglobulins are a heterogeneous group of proteins that are detectable in plasma and body fluids and on the surfaces of mucosal barriers and B lymphocytes. Although these proteins have multiple, diverse functions, they are classified as a family of proteins because of their capacity to act as antibodies-that is, to recognize and bind specifically to antigens. The rapid advances in understanding molecular structure and regulation, genetic diversity, and differences in functions of immunoglobulins have been reviewed recently (Bengten et al, 2000; Mix et al, 2006). The functions of immunoglobulins relevant to fetal and neonatal immunity are summarized in Table 36-2. Functions of individual immunoglobulin classes are different but overlapping (see Table 36-2) (Mix et al, 2006). Each immunoglobulin molecule contains two N-terminal, identical domains with antigen-binding activity (Fab). The Fab domains function to bind antigenic epitopes via complementarity determining regions. The principal functions of the Fc fragment include: receptor-mediated phagocytosis (IgG1/3 and IgA), cytotoxicity (IgG1/3), release of inflammatory mediators (IgE), receptor-mediated transport through mucosa (IgA and IgM) and placenta (IgG1/3), and complement activation (IgG1/3 and IgM). The five different isotype classes of human immunoglobulins (IgG, IgM, IgA, IgD, and IgE) are defined structurally by differences in the Fc fragments. Within isotypes, there are four IgG subclasses (IgG1, IgG2, IgG3, and IgG4) and two IgA subclasses (IgA1 and IgA2). Immunoglobulin G IgG is the most abundant immunoglobulin class in human serum and accounts for more than 75% of all antibody activity in this compartment. Its monomeric form circulates in plasma, has a molecular mass of approximately 155 kD, and in adults constitutes approximately 45% of total body IgG in the extravascular compartment.

Follow-up evaluation should include a multidisciplinary team approach involving a pediatric infectious diseases specialist treatments yeast infections pregnant discount 200 mg topiramate mastercard, pediatric otolaryngologist symptoms you have cancer generic topiramate 200 mg buy online, and child behavioraldevelopmental specialist treatment 3rd metatarsal stress fracture purchase topiramate 100 mg free shipping, in addition to a physical therapist treatment diffusion topiramate 100 mg buy amex, ophthalmologist medicine allergy purchase 200 mg topiramate, and neurologist as needed. Although almost two thirds of the treated infants had neutropenia, it was reversible when antiviral therapy was halted. All infants with documented congenital infection should have an ophthalmologic evaluation. If chorioretinitis is present, it should be managed in consultation with an ophthalmologist and infectious diseases expert. Other investigational studies including the assessment of the therapeutic potential in infants of the prodrug of ganciclovir, valganciclovir, are needed. Ganciclovir has demonstrated teratogenic risk in some studies (Schleiss and McVoy, 2004); although this has never been demonstrated in humans, it has limited research in this area. A case report of the use of oral ganciclovir in a pregnant liver transplant patient did not show any evidence of teratogenicity (Pescovitz, 1999). Of these potential mechanisms, the most common is via breast milk (Schleiss, 2006c), with transmission in the birth canal occurring less commonly. Approximately half of these infants were ill and exhibited symptoms such as hepatopathy, neutropenia, thrombocytopenia, and sepsislike deterioration. Proposed efforts to reduce the infectivity of breast milk from seropositive mothers have included freezing breast milk at ­20°C, Holder pasteurization, and short-term pasteurization (Hamprecht et al, 2004). Of these methods, freezing is the most studied and most likely to maintain the salutary immunologic properties of breast milk. When symptoms occur, they are nonspecific and vague, often described as a flulike syndrome. Potential manifestations include fever, fatigue, headache, myalgia, lymphadenitis, and pharyngitis, but these are the exception and not the rule. For several years after discovery, its role in disease was unclear, but it is now known to be the major etiologic agent of roseola infantum (exanthem subitum) and has been implicated in other clinical syndromes. Whether intrapartum transmission of these viruses can occur in the birth canal during delivery remains unknown. Perinatal transmission via this mechanism has been postulated (Joshi et al, 2000), but has not been demonstrated. This virus was assigned to the -herpesvirus family of the Herpesviridae, based on its molecular and sequence similarity to the other prototypical -herpesvirus, Epstein­Barr virus. Indeed, the routes of acquisition of infection and mechanisms responsible for person-to-person transmission remain uncertain. However, more recent evidence suggests that other routes of infection exist, including transmission by saliva (Pica and Volpi, 2007). There appears to be considerable regional variation in prevalence in the United States. In a population of children in south Texas, the seroprevalence was 26%, strongly suggesting that nonsexual modes of transmission predominate (Baillargeon et al, 2002). In Sub-Saharan Africa, prevalence in children is even higher, approaching 60% in some studies (Sarmati, 2004). The rash first appeared on the face and gradually spread to the trunk, arms, and legs. It initially consisted of discrete red macules that blanched with pressure and eventually became papular. An upper respiratory tract infection appeared as a secondary symptom in most children, and a lower respiratory tract infection appeared as a secondary symptom in one third of symptomatic children. Additional information on the epidemiology and modes of transmission of this pathogen, particularly in the prenatal and intrapartum period, is needed. In another study, placentas and some fetuses were studied in five cases of pregnancy interruption caused by maternal infectious mononucleosis in early gestation (Ornoy et al, 1982). Decidual lesions, consisting of perivasculitis and necrotizing deciduitis, were noted, and endovasculitis, perivasculitis, and occasional vascular obliteration were found in villi, as well as mononuclear and plasma cell infiltrates. The virus was identified in 1975 (Cossart et al, 1975) and was first linked to a disease in 1981-aplastic crisis in children with sickle cell anemia (Pattison et al, 1981). Primary infection with parvovirus B19 is commonly known as fifth disease or erythema infectiosum; it is classically described as a childhood exanthem with a "slapped cheek" appearance (Anderson et al, 1984). Considerable interest in the role of this virus in hydrops fetalis (nonimmune) and fetal aplastic crisis has evolved since the first cases of fetal death associated with maternal parvovirus B19 infection were reported in the 1980s (Brown et al, 1984; Kinney et al, 1988). A significant proportion of childbearing women are thus susceptible to infection (Markenson and Yancey, 1998; Yaegashi et al, 1998). Preconception seroprevalence to parvovirus B19 ranges from 24% to 84% (Ergaz and Ornoy, 2006). During pregnancy the risk of acquiring parvovirus B19 infection is low, ranging from 0% to 16. The risk of primary maternal infection is higher during epidemics, with reported seroconversion rates ranging between 3% (Kerr et al, 1994) and 34% (Woernle et al, 1987). It is estimated that one fourth to half of maternal parvovirus infections result in transmission of infection to the fetus (Alger, 1997; Gratacos et al, 1995; Koch et al, 1998). The vast majority of pregnancies are unaffected (Berry et al, 1992; Sheikh et al, 1992). There are conflicting reports regarding the prognosis once fetal infection has been established. A longitudinal study of fetal morbidity and mortality in more than 1000 women with primary parvovirus B19 infection in pregnancy demonstrated a risk of fetal hydrops of 3. A recent retrospective analysis of intrauterine parvovirus B19 infection at a single site suggested that the rate of adverse fetal outcome is much higher than previously appreciated, with fetal hydrops and demise occurring in greater than 10% of pregnancies (Beigi et al, 2008), although the total number of cases reported in this series was low; this primarily represented a referral population to a tertiary care center. Pathogenesis the most common mode of transmission of parvovirus B19 is via a respiratory route. Typically, once the virus establishes infection, viremia occurs, followed by mild systemic symptoms such as fever and malaise. Viremia is short-lived, lasting only 1 to 3 days, and the characteristic immunemediated rash develops 1 to 2 weeks later. Arthropathy caused by parvovirus B19 is common; it is observed more frequently in adults with primary infection than in children. It typically manifests late in the course of illness with acute onset of arthralgias or frank arthritis involving the hands, knees, wrists, and ankles. The symptoms usually subside within 1 to 3 weeks, although approximately 20% of affected women have persistent or recurring arthropathy for months to years (Woolf et al, 1989). Potential pathogenic mechanisms involve the recognized affinity of parvovirus B19 for progenitor erythroid cells of bone marrow. The blood group P antigen is a main cellular receptor for parvovirus B19, and it is found on red blood cells and on placental trophoblast cells (Jordan et al, 2001). The P antigen is also expressed on fetal cardiac myocytes, enabling parvovirus B19 to infect myocardial cells (Rouger et al, 1987) leading to myocarditis (von Kaisenberg et al, 2001). Myocarditis induced by parvovirus B19 can contribute to high-output cardiac failure, and the Epidemiology Parvovirus B19 infection is global in nature. The peak incidence of erythema infectiosum is in the late winter and early spring. The virus is spread by respiratory droplet (Anderson and Cohen, 1987), by blood products (especially pooled clotting factor concentrates; Jordan et al, 1998), and transplacentally (Ergaz and Ornoy, 2006). Fetal infection most likely occurs hematogenously via the placenta during maternal viremia. Parvovirus B19 infection in utero causes a pronormoblast arrest, which leads to fetal anemia, nonimmune hydrops, and sometimes progressive congestive heart failure (Ergaz and Ornoy, 2006; Kinney et al, 1988). The fetus is especially susceptible to adverse consequences of red blood cell infection, secondary to the intrinsic short fetal erythrocyte life span and rapidly expanding blood volume, especially during the second trimester. It has also been postulated that parvovirus B19 infection leads to cytotoxicity and subsequent anemia by inducing apoptosis of infected red blood cells (Yaegashi et al, 1999, 2000). In addition to erythroid precursors and myocytes, other organs appear to be involved in fetal parvovirus B19 infection. Neuropathologic findings in the infected hydropic fetus include perivascular calcifications, primarily in the cerebral white matter, as well as multinucleated giant cells. Data also suggest that the maternal cell­mediated immune response at the placental level contributes to the pathogenesis of congenital infection. Although some studies undertaken to examine the association between fetal infection and congenital anomalies failed to reveal any associations (Kinney et al, 1988; Mortimer et al, 1985), parvovirus B19 has increasingly been recognized as a cause of neuronal migration defects (Pistorius et al, 2008). The role of parvovirus B19 in neurodevelopmental injury has not been fully explored. There have been at least three case reports of fetal encephalopathy associated with in utero infection with parvovirus B19 (Alger, 1997). Consideration should be given to performing brain imaging studies in infants with symptomatic in utero parvovirus B19 infection. Two prospective studies in the United Kingdom of approximately 300 congenitally exposed infants found the risk of major congenital or developmental abnormality to be less than 1% (Miller et al, 1998). Parvovirus B19 has been implicated in some cases of congenital anemia (Heegaard and Brown, 2002). In light of these data, all infants undergoing evaluation for congenital anemias should be evaluated for the possibility of parvovirus B19 infection. Laboratory Evaluation In primary care, the diagnosis of human parvovirus B19 infection is most commonly made clinically through recognition of the characteristic rash. Serologic confirmation is necessary in high-risk situations, such as after a significant exposure of a pregnant woman to a child with erythema infectiosum. Both radioimmunoassays and enzyme-linked immunosorbent assays are available for detection of human parvovirus B19­specific IgG and IgM antibodies (Kinney and Kumar, 1988). Presence of anti­ parvovirus B19 IgM in fetal blood or amniotic fluid may confirm fetal infection, but may be detected in only one fifth of infected fetuses (Torok et al, 1992). False-positive results of parvovirus B19 IgM testing have been reported, including cross-reactions with anti-rubella IgM (Dieck et al, 1999). Monitoring of the pregnant patient with a primary parvovirus B19 infection is an important clinical problem. In the context of a human parvovirus B19 infection in a symptomatic, pregnant woman, elevated or rising weekly measurements of maternal alpha-fetoprotein suggest fetal infection, and rising concentrations may be a marker for an increased risk for hydrops fetalis (Carrington et al, 1987). However, some studies have failed to demonstrate any association between the magnitude of the elevation of the -fetoprotein and the severity of fetal anemia (Simms et al, 2009). Serial fetal ultrasonographic evaluations of infected Clinical Spectrum Parvovirus B19 infection causes erythema infectiosum, or fifth disease, in normal hosts, aplastic crisis in patients with hemolytic disorders, and chronic anemia in immunocompromised hosts. A substantial proportion of infected adult women may also have arthropathy in association with parvovirus B19 infection (Woolf et al, 1989). Maternal symptoms have been present in up to two thirds of documented cases of nonimmune hydrops fetalis associated with parvovirus B19 infection (Yaegashi et al, 1998). The major clinical presentation of parvovirus B19 infection in the fetus is hydrops fetalis. Various estimates suggest that human parvovirus B19 infection contributes from 10% to 27% of cases of nonimmune hydrops fetalis (Essary et al, 1998; Markenson and Yancey, 1998; Yaegashi et al, 1994). Parvovirus B19 does not appear to have a major role in intrauterine fetal demise in the absence of hydrops fetalis (Riipinen et al, 2008). The findings of echogenic bowel, ascites, pleural or pericardial effusion, or scalp edema are considered to be important markers of fetal infection and pathology. Middle cerebral artery Doppler to evaluate for fetal anemia may be another useful prospective surveillance tool, because fetal anemia can be detected using this technique before fetal hydrops is evident (Feldman et al, 2010). Other techniques to diagnose fetal parvovirus B19 infection have been studied and used, but most are not readily available. Virus can be cultured from tissue in suspension cultures of bone marrow cells from persons with hemolytic anemias, but it is difficult to isolate; therefore this method is not feasible for prenatal or postnatal diagnosis. Electron microscopy and histology have permitted visualization of parvovirus in fetal blood, ascitic fluid, tissue, and amniotic fluid, but the utility and sensitivity of these evaluations have not been well studied (Markenson and Yancey, 1998). Presumptive diagnosis can also be made based on finding IgM antibody in the maternal and fetal blood. One case-control study involving approximately 200 mother­infant pairs found no differences in frequency of developmental delay between infants born to women with confirmed primary parvovirus B19 infection during pregnancy and infants born to mothers with evidence of preconceptional immunity (Rodis et al, 1998b). Other studies have also suggested a favorable long prognosis in children born to women with primary parvovirus B19 infections during pregnancy (Miller et al, 1998). Prevention If a pregnant woman has a significant exposure to an infectious case of parvovirus B19, counseling should be provided regarding the potential risk of infection. Postexposure passive immunization with immunoglobulin is not currently recommended because the period of maternal viremia has passed by the time the diagnosis of acute parvovirus B19 infection is made (Boley and Popek, 1993). Human IgG monoclonal antibodies with potent neutralizing activity have been generated, and these are suggested as candidates for the development of immunotherapeutic approaches for individuals chronically infected with parvovirus B19 virus or for acutely infected pregnant women (Gigler et al, 1999), but these interventions are not commercially available. There has been limited progress in the development of a candidate parvovirus B19 vaccine. Phase 1 studies of a recombinant vaccine based on baculovirus-produced capsids have been conducted, and this vaccine was found to have a favorable safety and immunogenicity profile (Bansal et al, 1993). Efforts are under way to research and develop vaccines to prevent parvovirus B19 infections using other expression systems (Lowin et al, 2005). Pregnant health care providers should be counseled about the potential risks to their fetus from parvovirus B19 infections and should, at a minimum, wear masks and use standard droplet precautions when caring for immunocompromised patients with chronic parvovirus B19 infection or patients with parvovirus B19­induced aplastic crises. Some hospitals exclude pregnant health care providers from caring for these high-risk patients, but this issue remains controversial. Treatment Spontaneous resolution of fetal hydrops with normal neonatal outcome has been reported in approximately one third of cases (Humphrey et al, 1991; Rodis et al, 1998a; Sheikh et al, 1992). Because two thirds of fetuses do not recover without intervention, fetal transfusion is usually recommended (Boley and Popek, 1993; Brown et al, 1994).

In a regional program medications vs medicine 200 mg topiramate order otc, the specimens may be received by the state program and then delivered to the regional state or private laboratory medications used for depression topiramate 200 mg with visa, or they may be sent directly to the regional laboratory medications cause erectile dysfunction discount topiramate 100 mg on line. In either case symptoms flu buy topiramate toronto, the individual state programs serve as the state data and follow-up centers medicine song 2015 buy topiramate online pills. These small discs are then analyzed by various methodologies for the individual markers being sought. Hemoglobin electrophoresis of blood eluted from the filter paper disc is used for sickle cell disease screening. An enzyme assay is often used to screen for galactosemia and is always used to screen for biotinidase deficiency. Molecular assays are applied to quantify T cell receptor excision circles in dried blood to screen for severe combined immunodeficiency syndrome. More commonly, molecular assays are used to identify known mutations in certain disorders as a second-tier test. The final interpretation of the screening results is based on the primary analysis and, if available, the results of second-tier testing. However, it is important to realize that screening is not intended to be diagnostic; abnormal screening results must be supported by confirmatory investigations. These studies require additional specimens and are performed by clinical laboratories or sometimes by the screening laboratory. An elevation of an acylcarnitine could indicate an organic acid or fatty acid oxidation disorder. Any infant for whom such a screening result is reported should be evaluated by the primary care provider as soon as possible to facilitate the next steps towards the confirmation and management of the disorder. However, several conditions screened for are extremely rare, and primary health care professionals might not have sufficient information available to be able to direct appropriate intervention in screen-positive infants. Although all specimens with a metabolite concentration that crosses its threshold are considered screen-positive, all screen-positive results are not associated with the same likelihood of being associated with a disorder. Most infants with a positive screening result that is only mildly abnormal are less likely to have a disorder (see later discussion of false-positive results) than are infants with analyte concentrations that are several fold above the cutoff. Applying a uniform approach for all positive results in terms of urgency of intervention or battery of tests suggested can result in unnecessary parental anxiety and medical costs. However, if recommendations for further action and workup are customized in accordance with the potential significance of the abnormality, both parental anxiety and costs associated with false-positive results can be reduced. Accordingly, when an abnormality is identified, the original specimen is retested for the analyte that was abnormal. Additional tests can be performed by the screening laboratory to substantiate the finding and improve the specificity of screening (Matern et al, 2007; Rinaldo et al, 2006). In screening for congenital hypothyroidism, many programs initially measure T4 in the original newborn blood specimen. These sheets include information on disorders associated with the marker, estimated likelihood of being affected, clinical presentations of likely disorders, factors contributing to false positives, and recommendations for further management. The follow-up recommendations can range from immediate admission to a hospital, where further evaluation and therapy for the illness can be initiated without delay, to simply repeating the filter paper analysis on a sample collected a few days later. Other programs approach this problem differently, but with the same goal in mind, providing the primary care providers with the information needed to put the result in the appropriate context for the family. Any infant for whom an abnormal screening result is reported should be seen as soon as possible and evaluated with a careful history and physical examination. The infant may need to be admitted to the hospital where further evaluation and therapy for the illness can be initiated without delay. If the infant is active and alert with good feeding and shows no abnormal signs on initial evaluation, and the suspected disorder does not require immediate attention, a second filter paper blood specimen can be obtained and sent to the screening laboratory for repeated testing, or confirmatory testing can be performed on a less urgent basis. In many cases, confirmatory testing or referral to a specialist is required only if the second test indicates the presence of a disorder. In some programs, more specific confirmatory testing is the first response to a presumptive positive newborn screen, with a less intense time frame for individuals in whom the level of suspicion is lower. The physician should contact the screening laboratory when an infant whose screen has been reported as normal or whose screening results have not yet been reported has symptoms that suggest a metabolic disorder. If the testing has been completed and the newborn specimen is retained in storage, the laboratory may wish to recover the specimen and repeat the tests. The physician should also contact the screening laboratory for the results of repeated tests and inform the family of the results as soon as possible. There is no attempt to describe any of the disorders in detail or their rare variants. Screening relies on the detection of these elevated amino acids in the newborn specimen. The clinical manifestations may be a result of the toxic effects of the accumulating amino acid and metabolites produced by alternate pathways, a deficiency of the products of the normal pathway, or both. Liver disease, such as that associated with galactosemia, tyrosinemia type I or citrin deficiency, can also produce increased phenylalanine. If the screening level of phenylalanine is only slightly increased, retesting a second specimen before initiating a complete diagnostic work-up may suffice. Consequently, the finding of a substantially increased leucine level in the newborn blood specimen should prompt an immediate telephone call from the screening program to the attending physician. Confirmatory plasma and urine specimens should be obtained, and emergency therapy should be initiated. The urine specimen will test strongly positive for ketones and will contain large quantities of the branched-chain ketoacids and amino acids. A newborn with the intermediate variant might not have a blood leucine elevation, or the increase may be so mild as to be below the cutoff value. In the intermittent variant, the blood leucine concentration is normal in the newborn period, becoming elevated only in later infancy or childhood during acute metabolic episodes precipitated by febrile illness or surgery. Individuals with homocystinuria are clinically normal at birth but, if untreated, may develop ectopia lentis (dislocation of the lens), thromboembolism, osteoporosis, and mental retardation. The newborn blood screening marker for detecting homocystinuria is an increased level of methionine. Homocysteine can be measured as a second-tier analysis to improve specificity (Matern et al, 2007). The diagnosis of homocystinuria may be missed if the blood methionine concentration is not elevated at the time the newborn specimen is collected (Whiteman et al, 1979). Reducing the cutoff value for methionine can substantially increase the frequency of identified infants (Peterschmitt et al, 1999), but may also result in an increased number of false-positive results. Two additional rare disorders also produce hypermethioninemia: glycine-N-methyltransferase deficiency associated with liver disease (Luka et al, 2002; Mudd et al, 2001) and S-adenosylhomocysteine hydrolase deficiency, which may result in developmental delay and hypotonia (Baric et al, 2004). Confirmation of the disorder requires quantitative amino acid analyses of plasma and urine. In the infant with homocystinuria, homocystine is usually detectable in plasma and urine, plasma total homocysteine is increased as is methionine, and cystine is reduced. In isolated hypermethioninemia, methionine is markedly increased in plasma, but there is no detectable homocystine in plasma or urine and the plasma cystine concentration is normal. Hypermethioninemia secondary to liver disease owing to tyrosinemia type I, or to nonspecific liver disease, is usually accompanied by increased tyrosine. Citrullinemia and argininosuccinic acidemia produce hyperammonemia, often in the neonatal period, accompanied by poor feeding, tachypnea, lethargy, and vomiting. Discontinuation of protein and the provision of intravenous fluids with high caloric content are the first steps to take. L-Arginine or L-citrulline, as well as the "scavenger drugs" sodium phenylbutyrate and sodium benzoate, may be administered. Hemodialysis might be required to control the neurotoxic hyperammonemia, which can lead to irreversible brain damage, coma, and death. It is hoped that with early identification through newborn screening, patients with urea cycle disorders will be protected by presymptomatic therapy in the neonatal period. Arginase deficiency can also present acutely with hyperammonemia as described earlier, although more frequently it manifests as developmental delay and spastic diplegia in childhood with a milder degree of hyperammonemia (Crombez and Cederbaum, 2005). However, the preanalytic processing required for succinylacetone is more involved than that required for the amino acids and acylcarnitines. These programs may rely on elevations of tyrosine for identification of this disorder. Unfortunately, moderate elevations of tyrosine that are transient occur frequently in neonates, especially those who have low birthweights and are sick, necessitating frequent requests for repeated screening with virtually no detection of tyrosinemia type I. Unfortunately moderate transient elevations of tyrosine occur frequently in neonates, especially those who have low birthweights and are sick, necessitating frequent requests for repeated screening. Virtually no cases of tyrosinemia type I have been detected based on elevated tyrosine because almost all infants with tyrosinemia type I have had normal tyrosine levels when screened (Frazier et al, 2006). Consequently, the newborn detection of tyrosinemia type I by a tyrosine marker alone is ineffective. Tyrosinemia type I leads to liver and renal tubular disease and can later result in hepatocellular carcinoma. Medium-Chain Acyl-CoA Dehydrogenase Deficiency and Other Fatty Acid Oxidation Disorders the fatty acid oxidation disorders include those in which the long-chain fatty acids cannot traverse the mitochondrial membranes to be oxidized within the mitochondrial matrix. Fatty acid oxidation is essential to supply energy as adenosine triphosphate via the Krebs cycle and as ketones in the presence of a low supply of glucose. The disorders involving defective transport concern carnitine, whereas those with defective oxidation are named according to the enzyme that is deficient (see Table 27-1). The clinical consequence of these disorders is fasting intolerance resulting in hypoketotic hypoglycemia, lethargy, hyperammonemia, metabolic acidosis, hepatomegaly, and sometimes sudden death. Tragically, before newborn screening was available, this disorder was often diagnosed only retrospectively after a sudden unexplained death, usually when postmortem examination revealed a fatty liver. The treatment for fatty acid oxidation disorders is avoidance of fasting with high-carbohydrate, low-fat feedings and, of critical importance, prompt attention to acute illnesses in which vomiting occurs. Any infant with a fatty acid oxidation disorder should be evaluated at a metabolic center. Organic Acid Disorders Organic acid disorders are a heterogenous group of disorders with a combined frequency of approximately 1 in 50,000 (Zytkovicz et al, 2001). The marker for this disease group, as for the fatty acid oxidation disorders, is an abnormal acylcarnitine pattern. If a screening result suggests an organic acidemia, a metabolic specialist should be consulted immediately. The major organic acid disorders identified in newborn screening are propionic acidemia, the methylmalonic acidemias, and isovaleric acidemia. The organic acidemias can manifest in the neonatal period with a life-threatening, sepsis-like picture of feeding difficulties, lethargy, vomiting, and seizures. Metabolic acidosis virtually always accompanies this presentation, and hyperammonemia is common. In this situation, protein administration should be discontinued and replaced by administration of intravenous fluids with high caloric content and carnitine. The effects of early diagnosis and treatment on the clinical and neurologic development of individuals affected by an organic acid disorder are currently under investigation (Albers et al, 2001b). The enzyme assay identifies only galactosemia, whereas the metabolite assay also identifies other galactose metabolic disorders, such as deficiencies of galactokinase and epimerase. Severe neonatal liver disease and portosystemic shunting caused by anomalies in the portal system can also increase the galactose level. The most rapid confirmatory test for a positive result in galactosemia screening is urine testing for reducing substance. In almost all cases of severe galactosemia, this test produces a strongly positive reaction. If the urine contains reducing substance and the infant has clinical signs of galactosemia. Approximately 70% of the patients with galactosemia carry the Q188R mutation (Elsas and Lai, 1998). Nevertheless, urine-reducing substance may be absent in infants with clinically significant variants of galactosemia. Consequently, follow-up testing should be performed for all infants with an initial positive galactosemia screening result. Biotinidase Deficiency Biotin recycling is necessary for the maintenance of sufficient intracellular biotin to activate carboxylase enzymes. Lack of biotinidase activity results in reduced carboxylase activities and an organic acid disorder known as multiple carboxylase deficiency (Wolf and Heard, 1991). The clinical features of the disorder are developmental delay, seizures, hearing loss, alopecia, and dermatitis. Initiating biotin therapy in early infancy, when the disorder is presymptomatic, seems to prevent all the features of biotinidase deficiency. For this reason, a screening test has been developed and added to newborn screening in a number of newborn screening programs throughout the world (Hart et al, 1992). The frequency of identified newborns in these programs has a wide range, from 1:30,000 to 1:235,000. Almost all identified infants have been asymptomatic and have remained normal with biotin treatment. Galactosemia Galactosemia typically manifests in the neonatal period as failure to thrive, vomiting, and liver disease (Hughes et al, 2009). Death from bacterial sepsis, usually caused by Escherichia coli, occurs in a high percentage of untreated neonates (Levy et al, 1977). Some screening programs use a metabolite assay for total galactose (galactose and galactose-1-phosphate) to detect galactosemia. The major clinical features of untreated congenital hypothyroidism are growth retardation and delayed cognitive development leading to mental deficiency. If treatment with pharmacologic doses of T4 is initiated early, growth and mental development are normal. This situation may be due to a lack of the identifying marker abnormality at the time of specimen collection. Specifically, the T4 level during the first 24 hours of life in an affected infant might not yet be sufficiently decreased for identification because of persistence of maternally transmitted T4. The reported false-positive rates of screening for congenital hypothyroidism range from approximately 0.

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