Study of genetics, epidemiology, and vitamin usage in familial spina bifida in the United States in the 1990s

Neural tube defects: Risk factors and preventive measures

For the last 25 years, it has been proven that the occurrence or recurrence of neural tube defects can be prevented with the administration of folic acid before and early pregnancy. At present, over 80 countries in the world, except Japan, have mandated the fortification of wheat flour and/or rice with folic acid, which has resulted in a significant reduction in the prevalence of neural tube defects. In 2000, the Japanese government recommended folic acid 400 μg daily for young women of childbearing age and women who are planning to conceive. In 2002, the government started to present information about the importance of folic acid in the development of fetuses in the Mother-Child Health Booklet annually. Despite these endeavors, the prevalence of neural tube defects has remained unchanged. We discuss the risk factors of neural tube defects and propose preventive measures to decrease the number of neonates with neural tube defects. We believe that the government should implement the fortification of staple food with folic acid very soon, which will eventually decrease not only the neonatal mortality and morbidity, but also the economic burden on our health care system.

Spina Bifida: Pathogenesis, Mechanisms, and Genes in Mice and Humans

Spina bifida is among the phenotypes of the larger condition known as neural tube defects (NTDs). It is the most common central nervous system malformation compatible with life and the second leading cause of birth defects after congenital heart defects. In this review paper, we define spina bifida and discuss the phenotypes seen in humans as described by both surgeons and embryologists in order to compare and ultimately contrast it to the leading animal model, the mouse. Our understanding of spina bifida is currently limited to the observations we make in mouse models, which reflect complete or targeted knockouts of genes, which perturb the whole gene(s) without taking into account the issue of haploinsufficiency, which is most prominent in the human spina bifida condition. We thus conclude that the need to study spina bifida in all its forms, both aperta and occulta, is more indicative of the spina bifida in surviving humans and that the measure of deterioration arising from caudal neural tube defects, more commonly known as spina bifida, must be determined by the level of the lesion both in mouse and in man.

Risk factors for the occurrence of spina bifida (a case-control study) and the prevalence rate of spina bifida in Japan

BACKGROUND

The Japanese government recommended in 2000 that women planning pregnancy should take 400 μg of folic acid daily to decrease the risk of having an infant with spina bifida. We aimed to identify risk factors for the occurrence of spina bifida and to evaluate how the prevalence rate has altered over the past 3 decades.

METHODS

Subjects comprised 360 women who gave birth to spina bifida-affected offspring and 2333 women who gave birth to offspring without spina bifida between 2001 and 2012. A self-administered questionnaire was used to collect data, which were analyzed by multiple logistic regression models. The prevalence rate of spina bifida was obtained through data provided by international and domestic organizations.

RESULTS

Four variables were significantly associated with the increased risk of having newborns afflicted with spina bifida: not taking folic acid supplements (odds ratios [OR], 2.50; 95% confidence interval [CI], 1.72-3.64), presence of spina bifida patients within third-degree relatives (OR, 4.26; 95% CI, 1.12-16.19), taking anti-epileptic drugs without folic acid (OR, 20·20; 95% CI, 2.06-198.17), and low birth weight in the newborns ≤ 2500 g (OR, 4.21; 95% CI, 3.18-5.59). The prevalence rate of spina bifida has remained 5 to 6 per 10,000 total births and has not shown any decreasing trend over the past 11 years.

CONCLUSION

Four risk factors were identified among Japanese women. Because recommendations and information have not decreased the occurrence of spina bifida, the Japanese government should implement mandatory food fortification.

Clinical utility of folate-containing oral contraceptives

Folate is a generic term for a water-soluble B-complex vitamin which plays an important role in protein synthesis and metabolism and other processes related to cell multiplication and tissue growth. Pregnant and lactating women are at increased risk of folic acid deficiency because generally their dietary folate is insufficient to meet their physiological requirements and the metabolic demands of the growing fetus. The evidence pertaining to the reduction of the risk of neural tube defects (NTDs) due to folate is so compelling that supplementation with 400 μg of folic acid to all women trying to conceive until 12 weeks of pregnancy has been recommended by every relevant authority. A recent Cochrane review has also found protective effects of folate supplementation in occurrence and reoccurrence of NTDs. Despite food fortification and targeted public health campaigns promoting folic acid supplementation, 4,300,000 new cases occur each year worldwide resulting in an estimated 41,000 deaths and 2.3 million disability-adjusted life years (DALYS). This article will review the burden and risk factors of NTDS, and the role of folate in preventing NTDs. It will also describe different modes of supplementing folate and the newer evidence of the effectiveness of adding folate in oral contraceptives for raising serum and red blood cell folate levels.

Three generations of matrilineal excess of birth defects in Irish families with neural tube defects

BACKGROUND

Neural tube defects (NTDs) and birth defects overall are more likely to occur among maternal compared to paternal relatives in two generations (uncles/aunts and first cousins) of Irish families where an individual has been born with an NTD.

AIMS

The aim of this study was to determine if the matrilineal excess persisted into the third generation.

METHODS

First cousins were interviewed about their pregnancy outcomes and their offsprings' health.

RESULTS

Maternal first cousins once removed (FCOR) were more likely to have birth defects than paternal FCOR: 6.7 versus 3.5% (adjusted odds ratio 1.49, 95% CI 0.57, 3.89). No NTDs occurred. Folic acid supplementation significantly reduced the risk of birth defects (P = 0.04).

CONCLUSIONS

This study demonstrates an excess of birth defects among maternal relatives in three consecutive generations of NTD families, and supports the hypothesis that an underlying mechanism links distant maternal relatives in at least some NTD families.

Birth defects among maternal first cousins in Irish families with a neural tube defect

BACKGROUND

Maternal first cousins of an individual with a neural tube defect (NTD) are at increased risk for an NTD. It is not known if they are also at risk for other serious birth defects.

METHODS

We carried out an interview study of uncles and aunts and first cousins in Irish NTD families covering their pregnancy histories and the health of family members.

RESULTS

Maternal first cousins were more likely than paternal first cousins to have a birth defect (9.4% vs. 5.5%, p = 0.02; adjusted odds ratio: 1.72, 95% confidence interval: 1.04, 2.84).

CONCLUSIONS

This study shows that two generations of distant relatives (uncles/aunts and first cousins) in NTD families have similar maternal excesses of NTDs and birth defects overall. Inheritance mechanisms favouring matrilineal transmission, currently unknown, may contribute to birth defect occurrence in these families.

Maternal fumonisin exposure as a risk factor for neural tube defects

Fumonisins are mycotoxins produced by the fungus F. verticillioides, a common contaminant of maize (corn) worldwide. Maternal consumption of fumonisin B(1)-contaminated maize during early pregnancy has recently been associated with increased risk for neural tube defects (NTDs) in human populations that rely heavily on maize as a dietary staple. Experimental administration of purified fumonisin to mice early in gestation also results in an increased incidence of NTDs in exposed offspring. Fumonisin inhibits the enzyme ceramide synthase in de novo sphingolipid biosynthesis, resulting in an elevation of free sphingoid bases and depletion of downstream glycosphingolipids. Increased sphingoid base metabolites (i.e., sphinganine-1-phosphate) may perturb signaling cascades involved in embryonic morphogenesis by functioning as ligands for sphingosine-1-P (S1P) receptors, a family of G-protein-coupled receptors that regulate key biological processes such as cell survival/proliferation, differentiation and migration. Fumonisin-induced depletion of glycosphingolipids impairs expression and function of the GPI-anchored folate receptor (Folr1), which may also contribute to adverse pregnancy outcomes. NTDs appear to be multifactorial in origin, involving complex gene-nutrient-environment interactions. Vitamin supplements containing folic acid have been shown to reduce the occurrence of NTDs, and may help protect the developing fetus from environmental teratogens. Fumonisins appear to be an environmental risk factor for birth defects, although other aspects of maternal nutrition and genetics play interactive roles in determining pregnancy outcome. Minimizing exposures to mycotoxins through enhanced agricultural practices, identifying biomarkers of exposure, characterizing mechanisms of toxicity, and improving maternal nutrition are all important strategies for reducing the NTD burden in susceptible human populations.

Further evidence for a maternal genetic effect and a sex-influenced effect contributing to risk for human neural tube defects

BACKGROUND

Neural tube defects (NTDs), including spina bifida and anencephaly, are the second most common birth defect with an incidence of 1/1000. Genetic factors are believed to contribute to NTD risk and family-based studies can be useful for identifying such risk factors.

METHODS

We ascertained 1066 NTD families (1467 affected patients), including 307 multiplex NTD families. We performed pedigree analysis to describe the inheritance patterns, pregnancy outcomes, and recurrence risks to relatives of various types.

RESULTS

Myelomeningocele or spina bifida (66.9%) and cranial defects (17.7%) were the most common NTD subtypes observed. The overall male:female ratio for affected individuals was 0.82, and there were even fewer males among individuals with an upper level NTD (0.62). Among twins, 2 of the 5 monozygotic twins and only 3 of 35 dizygotic twins were concordant, while 27% of the same sex twins were concordant, but none of the different sex twins. The estimated 6.3% recurrence risk to siblings (CI 0.04-0.08) is consistent with previous reports. Families with two or more affected individuals show a higher proportion of female transmitters (p = 0.0002). Additionally, the number of affected relatives in maternal compared to paternal lineages was more than double (p = 0.006). There were significantly more miscarriages, infant deaths, and stillborn pregnancies of the maternal aunts and uncles (p < 0.0001) and of first cousins (p = 0.04).

CONCLUSIONS

Our data provide several lines of evidence consistent with a maternal effect, as well as a sex-influenced effect, in the etiology of NTDs.

[Accessibility of legal benefits available in Rio de Janeiro for physically handicapped people]

According to PAHO, only 2 % of Latin America's 85 million disabled people receive adequate medical care. Ten percent of the world's population lives with disabilities without having access to their constitutional rights. Disability must be addressed on several levels: medical, rehabilitative, social and political. Disability is strongly linked to poverty. Stigma, discrimination and inability to pay limit access to health services and education and ill-health increases the treatment cost, creating a vicious circle that must be broken. Although the Constitution grants rights to disabled persons including access to health and education, these legal benefits are not always obtained or respected. To better understand and address the problem, the process for obtaining three of these legal benefits was studied among disabled pediatric patients with myelomeningocele in a specialized Institute in Rio de Janeiro. Results show a low achievement rate. Bureaucracy and the expenses with locomotion were main constrains worsened by lack of time and resources in families struggling with poverty. Other difficulties were lack of professional attention and confidence in the system, problems related to documents, unqualified educational system and locomotion constrains.

A sensitive functional assay reveals frequent loss of genomic imprinting in human placenta

Loss of imprinting (LOI) is the gain of expression from the silent allele of an imprinted gene normally expressed from only one parental copy. LOI has been associated with neurodevelopmental disorders and reproductive abnormalities. The mechanisms of imprinting are varied, with DNA methylation representing only one. We have developed a functional transcriptional assay for LOI that is not limited to a single mechanism of imprinting. The method employs allele-specific PCR analysis of RT-PCR products containing common readout polymorphisms. With this method, we are able to measure LOI at the sensitivity of 1%. The method has been applied to measurement of LOI in human placentas. We found that RNA was stable in placentas stored for more than one hour at 4 degrees C following delivery. We analyzed a test panel of 26 genes known to be imprinted in the human genome. We found that 18 genes were expressed in placenta. Fourteen of the 18 expressed genes contained common readout polymorphisms in the transcripts with a minor allele frequency >20%. We found that 5 of the 14 genes were not imprinted in placenta. Using the remaining nine genes, we examined 93 heterozygosities in 27 samples. The range of LOI was 0%-96%. Among the 93 heterozygosities, we found 23 examples (25%) had LOI >3% and eight examples (9%) had LOI 1-3%. Our results indicate that LOI is common in human placentas. Because LOI in placenta is common, it may be an important new biomarker for influences on prenatal epigenetics.

Birth defects in uncles and aunts from Irish families with neural tube defects

BACKGROUND

Previous studies suggested an excess of matrilineal cases of neural tube defects among distant relatives in NTD families. There is little information on patterns of heredity of other birth defects among distant relatives.

METHODS

Between 1995 and 2003, 78 nuclear families and 373 uncles and aunts were interviewed about birth defects among uncles and aunts in Irish families with an NTD.

RESULTS

Among 783 total uncles and aunts, those related through the mother had more birth defects overall than those related through the father (8.4 vs. 4.0%, p = 0.01). The excess persisted after controlling with logistic regression models for maternal and paternal age, gender of uncle/aunt, proband's NTD diagnosis, and year of birth (OR 2.52; 95% CI: 1.29, 4.91; p = 0.007). Among individual birth defects, significant excesses over expected rates were seen for spina bifida, congenital heart defects, and syndactyly.

CONCLUSIONS

This study of reported birth defects suggests that maternal uncles and aunts in Irish families have significantly more birth defects than paternal uncles and aunts. These results, if confirmed, support the hypothesis that NTD relatives carry a susceptibility to other birth defects, preferentially on the mother's side of the family, suggesting opportunities for prevention. Birth Defects Research (Part A) 2008.

Congenital Abnormalities of the Thoracic and Lumbar Spine

Congenital spinal anomalies entail a wide spectrum of conditions that share in common some form of error during embryogenesis. Congenital disorders of the spine may not always be readily apparent at birth; they can present as a deformity with growth or with clinical signs of neurologic dysfunction early or later as an adolescent or adult. In this article the authors briefly summarize the embryology of the spine, which provides a background for understanding the pathophysiology of congenital spinal lesions. The discussion entails spine embryology and the developmental abnormalities commonly seen in the thoracolumbar spine.

Genetic variation in genes of folate metabolism and neural-tube defect risk

Neural-tube defects (NTD) are common congenital malformations that can lead to severe disability or even death. Periconceptional supplementation with the B-vitamin folic acid has been demonstrated to prevent 50-70% of NTD cases. Since the identification of the first genetic risk factor of NTD, the C677T single-nucleotide polymorphism (SNP) in the methylenetetrahydrofolate reductase (MTHFR) gene, and the observation that elevated plasma homocysteine levels are associated with NTD, research has focused on genetic variation in genes encoding for enzymes of folate metabolism and the closely-related homocysteine metabolism. In the present review relevant SNP in genes that code for enzymes involved in folate transport and uptake, the folate cycles and homocysteine metabolism are summarised and the importance of these SNP discussed in relation to NTD risk.

Candidate gene analysis in human neural tube defects

Biochemical and developmental pathways, mouse models, and positional evidence have provided numerous candidate genes for the study of human neural tube defects. In a survey of 80 studies on 38 candidate genes, few found significant results in human populations through case-control or family-based association studies. While the folate pathway has been explored extensively, only the MTHFR 677C > T polymorphism was significant, and only in an Irish population. Developmental pathways such as the Wnt signaling pathway and Hox genes have also been explored without positive results. More than 90 mouse candidates have been identified through spontaneous and knockout mutations, but only the T locus (mouse Brachyury gene) showed association in an initial study that was not confirmed on follow-up. Positional candidates have been derived from cytogenetic evidence, but preliminary genomic screens have limited power due to small sample sizes. Future studies would increase their power to detect association by using more samples. In addition a clarification of the phenotype would be beneficial as many studies used different inclusion criteria. Incorporating several types of data could highlight better candidates, as would looking beyond the traditional sources for candidate genes. Recent studies of an energy metabolism gene (UCP2) and vitamin B metabolism (Transcoalbumin) have produced promising results. Utilizing other model organisms may also be beneficial, as in a recent study from a chick model of NTDs in NCAM1. New approaches combined with traditional methods and increased sample sizes will help prioritize human NTD candidate genes and clarify the complex etiology of this condition.

Human neural tube defects: developmental biology, epidemiology, and genetics

Birth defects (congenital anomalies) are the leading cause of death in babies under 1 year of age. Neural tube defects (NTD), with a birth incidence of approximately 1/1000 in American Caucasians, are the second most common type of birth defect after congenital heart defects. The most common presentations of NTD are spina bifida and anencephaly. The etiologies of NTDs are complex, with both genetic and environmental factors implicated. In this manuscript, we review the evidence for genetic etiology and for environmental influences, and we present current views on the developmental processes involved in human neural tube closure.

Whole genomewide linkage screen for neural tube defects reveals regions of interest on chromosomes 7 and 10

Neural tube defects (NTDs) are the second most common birth defects (1 in 1000 live births) in the world. Periconceptional maternal folate supplementation reduces NTD risk by 50-70%; however, studies of folate related and other developmental genes in humans have failed to definitively identify a major causal gene for NTD. The aetiology of NTDs remains unknown and both genetic and environmental factors are implicated. We present findings from a microsatellite based screen of 44 multiplex pedigrees ascertained through the NTD Collaborative Group. For the linkage analysis, we defined our phenotype narrowly by considering individuals with a lumbosacral level myelomeningocele as affected, then we expanded the phenotype to include all types of NTDs. Two point parametric analyses were performed using VITESSE and HOMOG. Multipoint parametric and nonparametric analyses were performed using ALLEGRO. Initial results identified chromosomes 7 and 10, both with maximum parametric multipoint lod scores (Mlod) >2.0. Chromosome 7 produced the highest score in the 24 cM interval between D7S3056 and D7S3051 (parametric Mlod 2.45; nonparametric Mlod 1.89). Further investigation demonstrated that results on chromosome 7 were being primarily driven by a single large pedigree (parametric Mlod 2.40). When this family was removed from analysis, chromosome 10 was the most interesting region, with a peak Mlod of 2.25 at D10S1731. Based on mouse human synteny, two candidate genes (Meox2, Twist1) were identified on chromosome 7. A review of public databases revealed three biologically plausible candidates (FGFR2, GFRA1, Pax2) on chromosome 10. The results from this screen provide valuable positional data for prioritisation of candidate gene assessment in future studies of NTDs.

An intervention study to increase knowledge and use of folic acid among relatives in neural tube defect-affected families in Washington, D.C

BACKGROUND

Little is known about the level of knowledge and use of folic acid among near relatives in U.S. families of a child with spina bifida. We hypothesized that relatives would be more knowledgeable than the general population and more likely to take folic acid. Further, we hypothesized that relatives would be more motivated by an intervention to increase their use of folic acid.

METHODS

We conducted an intervention study among females in families attending a hospital spina bifida clinic in Washington, DC.

RESULTS

The 231 subjects consisted of the affected individuals, mothers, sisters, and aunts. The average age was 34 years. At baseline, most (87.4%) reported that they had heard of folic acid; 37.6% were currently taking multivitamins with folic acid and 6.9% were taking folic acid tablets. The intervention significantly increased both knowledge (to 99%) and intake of folic acid from 41.9 to 48.5%. Folic acid intake increased significantly among African-American women and women with less education, women who were older, married, with children, and nonsmokers.

CONCLUSIONS

This intervention was successful in increasing folic acid intake among female relatives in spina bifida-affected families. By the end of the study, almost all women had heard of folic acid and folic acid use had increased by 16%. Among these women at higher than expected risk for having an affected child, this rate of intake, while more than the general population, still falls short of optimum. Fortification of food with folic acid may be the only way to ensure increased folic acid intake.

Epidemiology of neural tube defects and folic acid

This review article combines four disparate observations about Neural Tube Defects (NTDs). They are the worldwide decline in the birth incidence that began prior to prenatal diagnosis; family recurrence risks; the effect of prenatal diagnosis and termination of affected pregnancies; and the effect of folic acid.

Folic acid knowledge and use among relatives in Irish families with neural tube defects: an intervention study

BACKGROUND

Relatives in families where a child has a neural tube defect (NTD) may be at higher risk of having an affected child. Little is known of their level of knowledge and use of folic acid.

AIM

To carry out an intervention study intended to increase knowledge and use of folic acid among relatives.

METHODS

One hundred aunts and female first cousins (relatives of the proband) were interviewed by telephone before and after receiving an information pack.

RESULTS

At baseline, although knowledge of the benefits of folic acid was high (73%), use of folic acid was low (8.8%). After the intervention, knowledge increased and use went up to 19% (p < 0.05).

CONCLUSIONS

This study suggests that relatives in Irish NTD families have a high level of information about folic acid benefits. This awareness may not translate into action since the intervention produced only a modest increase in folic acid use overall. Future studies focussing on women who are planning a pregnancy may show larger benefits from intervention.

Birth order and neural tube defects: a reappraisal

There is evidence that late birth order is associated with some complex disorders. For neural tube defects (NTDs) there is no consensus as to whether first or increased birth order is associated or not. A meta-analysis of published data on NTDs was carried out to ascertain whether there is an increased risk for children first born or of high birth order to have NTDs. All data available with information regarding the frequency of live births and NTDs cases by birth order (1, 2, 3, and 4 or more) were included in the analysis. Effect sizes calculations were performed. Children with higher birth order are more likely to have spina bifida but not anencephaly. This same effect was also seen for all NTDs combined, which probably reflects the association with spina bifida. These results suggest the compilation of anencephaly and spina bifida data can be the explanation for the controversies seen in the literature.

Epidemiology of neural tube defects

Neural tube defects (NTDs)-malformations secondary to abnormal neural tube closure between the third and fourth weeks of gestational age-have a complex and imperfectly understood etiology in which both genetic and environmental factors appear to be involved. A number of specific chromosomal or single-gene disorders, presumably not affected by environmental influences, are associated with the development of NTDs, but such syndromal cases account for a small proportion of NTDs in live-born infants. Analysis of recurrence patterns within families and of twin-concordance data provides evidence of a genetic influence in nonsyndromal cases, but factors such as socioeconomic status and geographic area (independent of race or ethnicity) are also associated with variations in the incidence of NTDs. The prevalence at birth of both anencephaly and spina bifida has decreased, but the advent of antenatal diagnosis and elective termination of affected pregnancies has undermined the reliability of birth prevalence rate as an estimate of incidence. Some occupational and other exposures, including maternal use of antiepileptic drugs (AEDs), are associated with increased risk for NTDs. Among women who have had an NTD-affected pregnancy, recurrence risk is markedly higher than the risk for a first NTD-affected pregnancy in the general population. There is strong evidence, overall, for a protective effect of adequate folate consumption. In some high-risk groups, however, such as women taking AEDs, folate supplementation has not been proven to reduce NTD risk.

Folate, homocysteine and neural tube defects: an overview

Folate administration substantially reduces the risk on neural tube detects (NTD). The interest for studying a disturbed homocysteine (Hcy) metabolism in relation to NTD was raised by the observation of elevated blood Hcy levels in mothers of a NTD child. This observation resulted in the examination of enzymes involved in the folate-dependent Hcy metabolism. Thus far, this has led to the identification of the first and likely a second genetic risk factor for NTD. The C677T and A1298C mutations in the methylenetetrahydrofolate reductase (MTHFR) gene are associated with an increased risk of NTD and cause elevated Hcy concentrations. These levels can be normalized by additional folate intake. Thus, a dysfunctional MTHFR partly explains the observed elevated Hcy levels in women with NTD pregnancies and also, in part, the protective effect of folate on NTD. Although the MTHFR polymorphisms are only moderate risk factors, population-wide they may account for an important part of the observed NTD prevalence.

Spina bifida and other neural tube defects

NTDs, resulting from failure of the neural tube to close during the fourth week of embryogenesis, are the most common severely disabling birth defects in the United States, with a frequency of approximately 1 of every 2000 births. Neural tube malformations involving the spinal cord and vertebral arches are referred to as spina bifida, with severe types of spina bifida involving protrusion of the spinal cord and/or meninges through a defect in the vertebral arch. Depending on the level of the lesion, interruption of the spinal cord at the site of the spina bifida defect causes paralysis of the legs, incontinence of urine and feces, anesthesia of the skin, and abnormalities of the hips, knees, and feet. Two additional abnormalities often seen in children with spina bifida include hydrocephalus and the Arnold-Chiari type II malformation. Despite the physical and particular learning disabilities children with spina bifida must cope with, participation in individualized educational programs can allow these children to develop skills necessary for autonomy in adulthood. Advances in research to uncover the molecular basis of NTDs is enhanced by knowledge of the link between both the environmental and genetic factors involved in the etiology of NTDs. The most recent development in NTD research for disease-causing genes is the discovery of a genetic link to the most well-known environmental cause of neural tube malformation, folate deficiency in pregnant women. Nearly a decade ago, periconceptional folic acid supplementation was proven to decrease both the recurrence and occurrence of NTDs. The study of folate and its association with NTDs is an ongoing endeavor that has led to numerous studies of different genes involved in the folate metabolism pathway, including the most commonly studied thermolabile mutation (C677T) in the MTHFR gene. An additional focus for NTD research involves mouse models that exhibit both naturally occurring NTDs, as well as those created by experimental design. We hope the search for genes involved in the risk and/or development of NTDs will lead to the development of strategies for prevention and treatment. The most recent achievement in treatment of NTDs involves the repair of meningomyelocele through advancements in fetal surgery. Convincing experimental evidence exists that in utero repair preserves neurologic function, as well as resolving the hydrocephalus and Arnold-Chiari malformation that often accompany meningomyelocele defects. However, follow-up is needed to completely evaluate long-term neurologic function and overall improved quality of life. And in the words of Olutoye and Adzick, "until the benefits of fetal [meningomyelocele] repair are carefully elucidated, weighed against maternal and fetal risks, and compared to conventional postnatal therapy, this procedure should be restricted to a few centers that are committed (clinically and experimentally) to investigating these issues."

Natural rubber latex allergy: spectrum, diagnostic approach, and therapy

Latex allergy has reached epidemic proportions in the United States and is increasingly recognized as a significant contributor to morbidity and mortality during medical and surgical procedures. Ultimately, many of the affected patients with recognized latex sensitivity and those who are not yet diagnosed will receive treatment for their allergic reactions to latex in emergency departments. Consequently, emergency physicians must have a comprehensive understanding of the etiology, epidemiology, pathogenesis, treatment, and management of these challenging patients. Groups at high risk include spina bifida cystica patients, health care workers, latex industry workers, specific food-allergy patients, and patients with a history of atopy or multiple surgical procedures. Sensitization to latex antigens is commonly encountered in health care workers wearing latex gloves with high latex allergen concentrations and in workers using powdered latex surgical gloves. Exposure to air-borne allergens and water-soluble IgE reactive latex antigens from natural rubber latex products in sensitized individuals can result in type I (immediate) hypersensitivity reactions. Clinical manifestations include contact urticaria, dermatitis, allergic rhinitis, conjunctivitis, asthma, angioedema, and anaphylaxis. Diagnostic tools include serological assays and skin prick testing. At present, latex avoidance is the only available treatment and is the key to preventing allergic reactions in latex-sensitized individuals. Health care worker sensitization to latex antigens in natural rubber products is becoming an increasing contributor to workers' liability and disability claims. Specific action can be taken to reduce occupational and patient exposure to latex antigens.

Erythrocyte antioxidant enzyme activities in children with myelomeningocele

Erythrocyte free radical scavenging enzyme activities and their cofactor trace elements in plasma were assessed in 26 selected patients with myelomeningocele, both parents from 10 selected families, and 14 healthy adult controls. All index children except one were deficient in erythrocyte glutathione peroxidase (GSH-Px). Nine of 10 parent pairs had at least one parent with deficient GSH-Px activity. Children with myelomeningocele had significantly lower GSH-Px activities than their parents; the group of 10 parent pairs had significantly lower GSH-Px activities than the control group; and glutathione reductase activities were significantly lower in parents and children with myelomeningocele compared with controls. A deficiency in one or more antioxidant enzymes may increase the risk for neural tube defects.

Parents do matter: genomic imprinting and parental sex effects in neurological disorders

Genomic imprinting is a recently recognized phenomenon of differential expression of genetic material depending upon whether the genetic material has come from the male or female parent. This process of differential phenotypic expression involves mammalian development both in the normal and abnormal situations, resulting in parental sex effects. However, some parental sex effects may be due to other mechanisms such as mitochondrial inheritance. In the following article, evidence for genomic imprinting in experimental animals and in diseases are summarized. Relevant human neurological disorders manifesting parental sex effects discussed here include myotonic dystrophy, Huntington's disease, fragile X syndrome, spinocerebellar ataxia type 1, and neurofibromatosis type 1 and 2. A possible mechanism of imprinting involves the processes of methylation imprint and replication imprint. The knowledge of imprinting is helpful in clinical practice particularly in the areas of genetic counseling, prenatal diagnosis, and possible future gene therapy.

Absence of linkage between familial neural tube defects and PAX3 gene

Neural tube defects (NTD) are among the most common and disabling birth defects. The aetiology of NTD is unknown and their genetics are complex. The majority of NTD cases are sporadic, isolated, nonsyndromic, and generally considered to be multifactorial in origin. Recently, PAX3 (formerly HuP2, the human homologue of mouse Pax-3), on chromosome 2q35-37, was suggested as a candidate gene for NTD because mutations of Pax-3 cause the mouse mutant Splotch (Sp), an animal model for human NTD. Mutations in PAX3 were also identified in patients with Waardenburg syndrome type 1 (WS1). At least eight patients with both WS1 and NTD have been described suggesting pleiotropy or a contiguous gene syndrome. Seventeen US families and 14 Dutch families with more than one affected person with NTD were collected and 194 people (50 affected) from both data sets were genotyped using the PAX3 polymorphic marker. The data were analysed using affecteds only linkage analysis. The lod scores were -7.30 (US), -3.74 (Dutch), and -11.04 (combined) at theta = 0.0, under the assumption of the autosomal dominant model. For the recessive model, the lod scores were -3.30 (US), -1.46 (Dutch), and -4.76 (combined) at theta = 0.0. Linkage between PAX3 and familial NTD was excluded to 9.9 cM on either side of the gene for the dominant model and to 3.63 cM on either side of the gene for the recessive model in the families studied. No evidence of heterogeneity was detected using the HOMOG program. Our data indicate that PAX3 is not a major gene for NTD.