Risk of meningomyelocele mediated by the common 22q11.2 deletion

Meningomyelocele is one of the most severe forms of neural tube defects (NTDs) and the most frequent structural birth defect of the central nervous system. We assembled the Spina Bifida Sequencing Consortium to identify causes. Exome and genome sequencing of 715 parent-offspring trios identified six patients with chromosomal 22q11.2 deletions, suggesting a 23-fold increased risk compared with the general population. Furthermore, analysis of a separate 22q11.2 deletion cohort suggested a 12- to 15-fold increased NTD risk of meningomyelocele. The loss of Crkl, one of several neural tube-expressed genes within the minimal deletion interval, was sufficient to replicate NTDs in mice, where both penetrance and expressivity were exacerbated by maternal folate deficiency. Thus, the common 22q11.2 deletion confers substantial meningomyelocele risk, which is partially alleviated by folate supplementation.

Gastroschisis prevalence patterns in 27 surveillance programs from 24 countries, International Clearinghouse for Birth Defects Surveillance and Research, 1980-2017

BACKGROUND

Gastroschisis is a serious birth defect with midgut prolapse into the amniotic cavity. The objectives of this study were to evaluate the prevalence and time trends of gastroschisis among programs in the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR), focusing on regional variations and maternal age changes in the population.

METHODS

We analyzed data on births from 1980 to 2017 from 27 ICBDSR member programs, representing 24 countries and three regions (Europe+ (includes Iran) , Latin America, North America). Cases were identified using diagnostic codes (i.e., 756.7, 756.71, or Q79.3). We excluded cases of amniotic band syndrome, limb-body wall defect, and ruptured omphalocele. Programs provided annual counts for gastroschisis cases (live births, stillbirths, and legally permitted pregnancy terminations for fetal anomalies) and source population (live births, stillbirths), by maternal age.

RESULTS

Overall, gastroschisis occurred in 1 of every 3268 births (3.06 per 10,000 births; 95% confidence intervals [CI]: 3.01, 3.11), with marked regional variation. European+ prevalence was 1.49 (95%CI: 1.44, 1.55), Latin American 3.80 (95%CI: 3.69, 3.92) and North American 4.32 (95%CI: 4.22, 4.42). A statistically significant increasing time trend was observed among six European+ , four Latin American, and four North American programs. Women <20 years of age had the highest prevalence in all programs except the Slovak Republic.

CONCLUSIONS

Gastroschisis prevalence increased over time in 61% of participating programs, and the highest increase in prevalence was observed among the youngest women. Additional inquiry will help to assess the impact of the changing maternal age proportions in the birth population on gastroschisis prevalence.

A multi-program analysis of cleft lip with cleft palate prevalence and mortality using data from 22 International Clearinghouse for Birth Defects Surveillance and Research programs, 1974-2014

BACKGROUND

Cleft lip with cleft palate (CLP) is a congenital condition that affects both the oral cavity and the lips. This study estimated the prevalence and mortality of CLP using surveillance data collected from birth defect registries around the world.

METHODS

Data from 22 population- and hospital-based surveillance programs affiliated with the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) in 18 countries on live births (LB), stillbirths (SB), and elective terminations of pregnancy for fetal anomaly (ETOPFA) for CLP from 1974 to 2014 were analyzed. Prevalence and survival (survival for LB only) estimates were calculated for total and subclassifications of CLP and by pregnancy outcome.

RESULTS

The pooled prevalence of total CLP cases was 6.4 CLP per 10,000 births. The prevalence of CLP and all of the pregnancy outcomes varied across programs. Higher ETOPFA rates were recorded in most European programs compared to programs in other continents. In programs reporting low ETOPFA rates or where there was no ascertainment of ETOPFA, the rate of CLP among LB and SB was higher compared to those where ETOPFA rates were ascertained. Overall survival for total CLP was 91%. For isolated CLP, the survival was 97.7%. CLP associated with multiple congenital anomalies had an overall survival of 77.1%, and for CLP associated with genetic/chromosomal syndromes, overall survival was 40.9%.

CONCLUSIONS

Total CLP prevalence reported in this study is lower than estimates from prior studies, with variation by pregnancy outcomes between programs. Survival was lower when CLP was associated with other congenital anomalies or syndromes compared to isolated CLP.

Prevalence and mortality among children with anorectal malformation: A multi-country analysis

PURPOSE

We examined the total prevalence, trends in prevalence, and age-specific mortality among individuals with anorectal malformation (ARM) METHODS: We conducted a retrospective cohort study using data from 24 population- and hospital-based birth defects surveillance programs affiliated with the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) from 18 countries and for births from 1974 to 2014. We estimated pooled and program-specific total prevalence per 10,000 total births. Poisson regression was used to assess time trends in prevalence from 2001 to 2012 when most programs contributed data. We calculated selected age-specific proportions of deaths, stratified by case status RESULTS: The pooled total prevalence of ARM was 3.26 per 10,000 total births (95% Confidence Interval = 3.19, 3.32) for birth years 1974-2014. About 60% of cases were multiple or syndromic. Prevalence of multiple, syndromic, and stillborn cases decreased from 2001 to 2012. The first week mortality proportion was 12.5%, 3.2%, 28.3%, and 18.2% among all, isolated, multiple, and syndromic cases, respectively CONCLUSIONS: ARM is relatively rare, with multiple and syndromic cases showing decreasing prevalence during the study period. Mortality is a concern during the first week of life, and especially among multiple and syndromic cases. Our descriptive epidemiological findings increase our understanding of geographic variation in the prevalence of ARM and can be used to plan needed clinical services. Exploring factors influencing prevalence and mortality among individuals with ARM could inform future studies.

Severe Congenital Neutropenia Type 4: A Rare Disease Harboring a G6pc3 Gene Pathogenic Variant Particular to the Mexican Population

Background

Severe congenital neutropenia type 4 (SCN4) is a rare autosomal recessive granulopoiesis disorder caused by G6PC3 gene pathogenic variants. The estimated prevalence is 1/10,000,000 people. Over 90% of patients present a syndromic form with variable multisystemic involvement, including congenital heart defects, increased visibility of superficial veins (IVSV), inflammatory bowel disease, and congenital urogenital defects as prominent symptoms.

Objectives

The objective of the study was to study non-hematological phenotypic findings that suggest a clinical diagnosis of SCN4.

Methods

We examined medical records of patients diagnosed with neutropenia from January 2000 to December 2020, selecting cases with non-hematologic manifestations for phenotypic description and G6PC3 gene sequencing.

Results

We found 11 cases with non-hematologic features: congenital heart defects in 8, IVSV in 6, inflammatory bowel disease in 4, urogenital defects in 4, and similar facial appearance. In addition, Sanger sequencing confirmed 3 homozygous cases for the c.210delC variant, a compound heterozygous harboring this variant, and a c.199_218+1 deletion.

Conclusions

Our findings of the c.210delC variant in very close geographical settings, to date, have only been reported among Mexicans, and a mutual uncommon surname in two families strongly supports a founder effect for the variant in the studied population. Furthermore, the described non-hematologic symptoms in patients with severe primary neutropenia should be explored, confirming SCN4 by investigating G6PC3 gene mutations.

Telomeres Length Variations in a Rheumatoid Arthritis Patients Cohort at Early Disease Onset and after Follow-Up

Background

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovial joint inflammation, progressive disability, premature immune aging, and telomere length (TL) shortening.

Objectives

The objective of the study was to study TL changes in patients at early disease onset and after follow-up.

Methods

Relative leukocyte TL (rLTL) was measured by quantitative polymerase chain reaction (qPCR) in 88 at-admission patients (AAP) with < 1 year of symptoms onset, self-compared after follow-up, and a reference group of sex- and age-matched healthy individuals. Correlations between rLTL percentage change after variable disease exposure time (DET) and clinical laboratory disease activity markers and treatments were assessed. Non-parametrical statistics were applied, considering < 0.05 p-value significant.

Results

The median (p25, p75) rLTL was lower in patients after DET (0.61, 0.49-0.70) than in AAP (0.64, 0.50-0.77), p = 0.017. Furthermore, telomeres at early stages of RA were shorter than in the reference group (0.77, 0.59-0.92; p = 0.003). HLA-DRB1*04 allele carrier status did not significantly affect rLTL at an early stage and after follow-up. The patients' rLTL shortening was mainly associated with longer at-admission telomeres (OR 16.2, 95%CI: 3.5-74.4; p < 0.0001).

Conclusions

At follow-up, RA patients showed significantly shorter rLTL than AAP, particularly in those AAP with longer telomeres, disregarding disease activity and treatments, denoting an rLTL shortening effect influenced by age, DET, and native rLTL.

A Multicountry Analysis of Prevalence and Mortality among Neonates and Children with Bladder Exstrophy

OBJECTIVE

 Bladder exstrophy (BE) is a rare but severe birth defect affecting the lower abdominal wall and genitourinary system. The objective of the study is to examine the total prevalence, trends in prevalence, and age-specific mortality among individuals with BE.

STUDY DESIGN

 We conducted a retrospective cohort study. Data were analyzed from 20 birth defects surveillance programs, members of the International Clearinghouse for Birth Defects Surveillance and Research in 16 countries. Live births, stillbirths, and elective terminations of pregnancy for fetal anomaly (ETOPFA) diagnosed with BE from 1974 to 2014. Pooled and program-specific prevalence of BE per 100,000 total births was calculated. The 95% confidence intervals (CI) for prevalence were estimated using Poisson approximation of binomial distribution. Time trends in prevalence of BE from 2000 to 2014 were examined using Poisson regression. Proportion of deaths among BE cases was calculated on the day of birth, day 2 to 6, day 7 to 27, day 28 to 364, 1 to 4 years, and ≥5 years. Mortality analysis was stratified by isolated, multiple, and syndromic case status.

RESULTS

 The pooled total prevalence of BE was 2.58 per 100,000 total births (95% CI = 2.40, 2.78) for study years 1974 to 2014. Prevalence varied over time with a decreasing trend from 2000 to 2014. The first-week mortality proportion was 3.5, 17.3, and 14.6% among isolated, multiple, and syndromic BE cases, respectively. The majority of first-week mortality occurred on the first day of life among isolated, multiple, and syndromic BE cases. The proportion of first-week deaths was higher among cases reported from programs in Latin America where ETOPFA services were not available.

CONCLUSIONS

 Prevalence of BE varied by program and showed a decreasing trend from 2000 to -2014. Mortality is a concern among multiple and syndromic cases, and a high proportion of deaths among cases occurred during the first week of life.

KEY POINTS

· Total prevalence of BE was 2.58 per 100,000 births.. · Prevalence decreased from 2000 to 2014.. · The first-week mortality was 9.3%..

GMPPA defects cause a neuromuscular disorder with α-dystroglycan hyperglycosylation

GDP-mannose-pyrophosphorylase-B (GMPPB) facilitates the generation of GDP-mannose, a sugar donor required for glycosylation. GMPPB defects cause muscle disease due to hypoglycosylation of α-dystroglycan (α-DG). Alpha-DG is part of a protein complex, which links the extracellular matrix with the cytoskeleton, thus stabilizing myofibers. Mutations of the catalytically inactive homolog GMPPA cause alacrima, achalasia, and mental retardation syndrome (AAMR syndrome), which also involves muscle weakness. Here, we showed that Gmppa-KO mice recapitulated cognitive and motor deficits. As structural correlates, we found cortical layering defects, progressive neuron loss, and myopathic alterations. Increased GDP-mannose levels in skeletal muscle and in vitro assays identified GMPPA as an allosteric feedback inhibitor of GMPPB. Thus, its disruption enhanced mannose incorporation into glycoproteins, including α-DG in mice and humans. This increased α-DG turnover and thereby lowered α-DG abundance. In mice, dietary mannose restriction beginning after weaning corrected α-DG hyperglycosylation and abundance, normalized skeletal muscle morphology, and prevented neuron degeneration and the development of motor deficits. Cortical layering and cognitive performance, however, were not improved. We thus identified GMPPA defects as the first congenital disorder of glycosylation characterized by α-DG hyperglycosylation, to our knowledge, and we have unraveled underlying disease mechanisms and identified potential dietary treatment options.

Survival of infants born with esophageal atresia among 24 international birth defects surveillance programs

BACKGROUND

Esophageal atresia (EA) affects around 2.3-2.6 per 10,000 births world-wide. Infants born with this condition require surgical correction soon after birth. Most survival studies of infants with EA are locally or regionally based. We aimed to describe survival across multiple world regions.

METHODS

We included infants diagnosed with EA between 1980 and 2015 from 24 birth defects surveillance programs that are members of the International Clearinghouse for Birth Defects Surveillance and Research. We calculated survival as the proportion of liveborn infants alive at 1 month, 1- and 5-years, among all infants with EA, those with isolated EA, those with EA and additional anomalies or EA and a chromosomal anomaly or genetic syndrome. We also investigated trends in survival over the decades, 1980s-2010s.

RESULTS

We included 6,466 liveborn infants with EA. Survival was 89.4% (95% CI 88.1-90.5) at 1-month, 84.5% (95% CI 83.0-85.9) at 1-year and 82.7% (95% CI 81.2-84.2) at 5-years. One-month survival for infants with isolated EA (97.1%) was higher than for infants with additional anomalies (89.7%) or infants with chromosomal or genetic syndrome diagnoses (57.3%) with little change at 1- and 5-years. Survival at 1 month improved from the 1980s to the 2010s, by 6.5% for infants with isolated EA and by 21.5% for infants with EA and additional anomalies.

CONCLUSIONS

Almost all infants with isolated EA survived to 5 years. Mortality was higher for infants with EA and an additional anomaly, including chromosomal or genetic syndromes. Survival improved from the 1980s, particularly for those with additional anomalies.

Myelomeningocele genotype-phenotype correlation findings in cilia, HH, PCP, and WNT signaling pathways

BACKGROUND

Myelomeningocele (MMC) is the most severe and frequent type of spina bifida. Its etiology remains poorly understood. The Hedgehog (Hh), Wnt, and planar cell polarity (PCP) signaling pathways are essential for normal tube closure, needing a structural-functional cilium for its adequate function. The present study aimed to investigate the impact of different gene variants (GV) from those pathways on MMC genotype-subphenotype correlations.

METHODS

The study comprised 500 MMC trios and 500 controls, from 16 Telethon centers of 16 Mexican states. Thirty-four GVs of 29 genes from cilia, Hh, PCP, and Wnt pathways, were analyzed, by an Illumina on design microarray. The total sample (T-MMC) was stratified in High-MMC (H-MMC) when thoracic and Low-MMC (L-MMC) when lumbar-sacral vertebrae affected. STATA/SE-12.1 and PLINK software were used for allelic association, TDT, and gene-gene interaction (GGI) analyses, considering p value <.01 as statistically significant differences (SSD).

RESULTS

Association analysis showed SSD for COBL-rs10230120, DVL2-rs2074216, PLCB4-rs6077510 GVs in T-MMC and L-MMC, and VANGL2-rs120886448 in T-MMC and H-MMC, and INVS-rs7024375 exclusively in L-MMC. TDT assay showed SSD preferential transmissions of C2CD3-rs826058 in H-MMC, and LRP5-rs3736228, and BBS2-rs1373 in L-MMC. Statistically significant GGI was observed in four in T-MMC, four completely different in L-MMC, and one in H-MMC. Interestingly, no one repeated in subphenotypes.

CONCLUSIONS

Our results support an association of GVs in Hh, Wnt, PCP, and cilia pathways, with MMC occurrence location, although further validation is needed. Furthermore, present results show a distinctive panel of gene-variants in H-MMC and LMMC subphenotypes, suggesting a feasible genotype-phenotype correlation.

Prevalence and mortality in children with congenital diaphragmatic hernia: a multicountry study

PURPOSE

This study determined the prevalence, mortality, and time trends of children with congenital diaphragmatic hernia (CDH).

METHODS

Twenty-five hospital- and population-based surveillance programs in 19 International Clearinghouse for Birth Defects Surveillance and Research member countries provided birth defects mortality data between 1974 and 2015. CDH cases included live births, stillbirths, or elective termination of pregnancy for fetal anomalies. Prevalence, cumulative mortality rates, and 95% confidence intervals (CIs) were calculated using Poisson regression and a Kaplan-Meier product-limit method. Joinpoint regression analyses were conducted to assess time trends.

RESULTS

The prevalence of CDH was 2.6 per 10,000 total births (95% CI: 2.5-2.7), slightly increasing between 2001 and 2012 (average annual percent change = 0.5%; 95% CI:-0.6 to 1.6). The total percent mortality of CDH was 37.7%, with hospital-based registries having more deaths among live births than population-based registries (45.1% vs. 33.8%). Mortality rates decreased over time (average annual percent change = -2.4%; 95% CI: -3.8 to 1.1). Most deaths due to CDH occurred among 2- to 6-day-old infants for both registry types (36.3%, hospital-based; 12.1%, population-based).

CONCLUSIONS

The mortality of CDH has decreased over time. Mortality remains high during the first week and varied by registry type.

Abstract P1-15-02: An educational cancer genetics course to increase knowledge on hereditary breast cancer syndromes among physicians-in-training at a teaching hospital in Mexico City

Background: Breast cancer incidence is increasing globally, and a significant proportion of the disease has been linked to genetic susceptibility. Genetic knowledge and skills are essential for achieving optimal cancer care and prevention. However, in low- and middle-income countries the availability of physicians and other providers specializing in cancer genetics is very limited, and cancer genetics is not included in most undergraduate or graduate medical programs. Providing physicians-in-training with education on hereditary breast and ovarian cancer (HBOC) syndromes has the potential to improve the early identification of patients at a higher risk of breast cancer. This study aimed to assess the effect of a short HBOC course given to fellows from a single teaching hospital in Mexico City. Methods: We evaluated the basal practice patterns and knowledge on HBOC among fellows enrolled in internal medicine, general surgery, medical oncology and clinical genetics fellowship programs using a validated cancer genetics questionnaire composed of 13 questions and graded on a 0-100% scale. Fellows received a cancer genetics course (three lectures) from oncologists and geneticists with training in cancer genetics, and changes in knowledge post-course were evaluated using the same questionnaires. Descriptive statistics were utilized to describe the included subjects, and T-tests were used to compare pre and post questionnaire scores. Results: 110 fellows with a median age of 26.9 years (range 24-31) completed the basal questionnaire. 48.9% were enrolled in internal medicine, 21.8% in general surgery, 13.6% in medical oncology and 7.2% in clinical genetics. All respondents reported to routinely interrogate patients about their family history of cancer, and 70% said they had referred patients to the genetics clinic at their institution. The average score on the basal survey was 62% (SD 17). After the cancer genetics course was completed, 85 fellows answered the questionnaire. We found a relative increase in knowledge from pre to post-intervention of 12% (post-intervention average score 70% [SD 14]), which was statistically significant (p &lt;0.01). After the course, 36% of fellows said they would feel capable to provide recommendations to patients at risk of HBOC, compared to 17% before the course (p &lt;0.01). Conclusions: Although knowledge about HBOC among Mexican fellows is suboptimal, we found that providing short educational courses on cancer genetics may lead to a significant increase in knowledge on HBOC, as well as to an increase in confidence regarding recommendations. This study reinforces the need to develop focused and cost-effective educational strategies in low- and middle-income countries where specialists in cancer genetics are scarce, in order to provide physicians-in-training with knowledge and tools to recognize, refer, and counsel patients at risk of HBOC.

Citation Format: Yanin Chavarri Guerra, Hector De la Mora Molina, Rosa Elena Caballero Landinez, Arantxa Lagunas Salazar, Andrea De la O Murillo, Rafael Reyes Arciniega, Enrique Soto Perez de Celis, Jose Luis Rodriguez Olivares, Osvaldo M Mutchinick, Jazmin Arteaga Vazquez. An educational cancer genetics course to increase knowledge on hereditary breast cancer syndromes among physicians-in-training at a teaching hospital in Mexico City [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-15-02.

Analysis of Mortality among Neonates and Children with Spina Bifida: An International Registry-Based Study, 2001-2012

BACKGROUND

Medical advancements have resulted in better survival and life expectancy among those with spina bifida, but a significantly increased risk of perinatal and postnatal mortality for individuals with spina bifida remains.

OBJECTIVES

To examine stillbirth and infant and child mortality among those affected by spina bifida using data from multiple countries.

METHODS

We conducted an observational study, using data from 24 population- and hospital-based surveillance registries in 18 countries contributing as members of the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR). Cases of spina bifida that resulted in livebirths or stillbirths from 20 weeks' gestation or elective termination of pregnancy for fetal anomaly (ETOPFA) were included. Among liveborn spina bifida cases, we calculated mortality at different ages as number of deaths among liveborn cases divided by total number of liveborn cases with spina bifida. As a secondary outcome measure, we estimated the prevalence of spina bifida per 10 000 total births. The 95% confidence interval for the prevalence estimate was estimated using the Poisson approximation of binomial distribution.

RESULTS

Between years 2001 and 2012, the overall first-week mortality proportion was 6.9% (95% CI 6.3, 7.7) and was lower in programmes operating in countries with policies that allowed ETOPFA compared with their counterparts (5.9% vs. 8.4%). The majority of first-week mortality occurred on the first day of life. In programmes where information on long-term mortality was available through linkage to administrative databases, survival at 5 years of age was 90%-96% in Europe, and 86%-96% in North America.

CONCLUSIONS

Our multi-country study showed a high proportion of stillbirth and infant and child deaths among those with spina bifida. Effective folic acid interventions could prevent many cases of spina bifida, thereby preventing associated childhood morbidity and mortality.

PPP2R2B hypermethylation causes acquired apoptosis deficiency in systemic autoimmune diseases

Chronic inflammation causes target organ damage in patients with systemic autoimmune diseases. The factors that allow this protracted response are poorly understood. We analyzed the transcriptional regulation of PPP2R2B (B55ß), a molecule necessary for the termination of the immune response, in patients with autoimmune diseases. Altered expression of B55ß conditioned resistance to cytokine withdrawal-induced death (CWID) in patients with autoimmune diseases. The impaired upregulation of B55ß was caused by inflammation-driven hypermethylation of specific cytosines located within a regulatory element of PPP2R2B preventing CTCF binding. This phenotype could be induced in healthy T cells by exposure to TNF-α. Our results reveal a gene whose expression is affected by an acquired defect, through an epigenetic mechanism, in the setting of systemic autoimmunity. Because failure to remove activated T cells through CWID could contribute to autoimmune pathology, this mechanism illustrates a vicious cycle through which autoimmune inflammation contributes to its own perpetuation.

Isolated postaxial polydactyly: Epidemiologic characteristics from a multicenter birth defects study

Isolated postaxial polydactyly (I-PAP), as a single defect, is a frequent malformation, characterized by an extra digit placed on the ulnar or fibular side of the limbs. Worldwide prevalence varies from as high as 225/10,000 in Nigerians to so low as 6.08/10,000 in Argentinians. Genetic-ethnic background significantly affects worldwide prevalence and type of I-PAP. Herein we describe the epidemiological characteristics of I-PAP in 697 newborns, 383 males and 314 females identified in 1,178,993 examined live births from a multicenter case-control hospital-based population study, the Mexican program of Registry and Epidemiological Surveillance of Congenital Malformations (RYVEMCE). The main characteristics analyzed included total I-PAP, stratified in Types A and B, defined as complete or incomplete extra-digit formation, respectively, sex prevalence, affected limb, laterality, parity, prematurity, delivery-type, twinning, consanguinity, and parental age. Males (6.35/10,000) are significantly more frequently affected than females (5.45/10,000), hands more than feet, left more than right limbs, and Type B (74.50%) more than A (25.50%). Prematurity and forceps use were significantly more frequent in cases than controls. An evident decreasing time-trend prevalence was present. Similar findings with other studies were males, upper and left limbs more frequently affected. Findings that were not previously reported include prematurity, forceps use, a significant decreasing time trend and an inverse ethnic prevalence for Types A (75%) and B (25%) in the Mayan population in contrast to other worldwide ethnic groups.

Unexpected relevant role of gene mosaicism in patients with primary immunodeficiency diseases

BACKGROUND

Postzygotic de novo mutations lead to the phenomenon of gene mosaicism. The 3 main types are called somatic, gonadal, and gonosomal mosaicism, which differ in terms of the body distribution of postzygotic mutations. Mosaicism has been reported occasionally in patients with primary immunodeficiency diseases (PIDs) since the early 1990s, but its real involvement has not been systematically addressed.

OBJECTIVE

We sought to investigate the incidence of gene mosaicism in patients with PIDs.

METHODS

The amplicon-based deep sequencing method was used in the 3 parts of the study that establish (1) the allele frequency of germline variants (n = 100), (2) the incidence of parental gonosomal mosaicism in families with PIDs with de novo mutations (n = 92), and (3) the incidence of mosaicism in families with PIDs with moderate-to-high suspicion of gene mosaicism (n = 36). Additional investigations evaluated body distribution of postzygotic mutations, their stability over time, and their characteristics.

RESULTS

The range of allele frequency (44.1% to 55.6%) was established for germline variants. Those with minor allele frequencies of less than 44.1% were assumed to be postzygotic. Mosaicism was detected in 30 (23.4%) of 128 families with PIDs, with a variable minor allele frequency (0.8% to 40.5%). Parental gonosomal mosaicism was detected in 6 (6.5%) of 92 families with de novo mutations, and a high incidence of mosaicism (63.9%) was detected among families with moderate-to-high suspicion of gene mosaicism. In most analyzed cases mosaicism was found to be both uniformly distributed and stable over time.

CONCLUSION

This study represents the largest performed to date to investigate mosaicism in patients with PIDs, revealing that it affects approximately 25% of enrolled families. Our results might have serious consequences regarding treatment and genetic counseling and reinforce the use of next-generation sequencing-based methods in the routine analyses of PIDs.

A Novel GMPPA Mutation in Two Adult Sisters with Achalasia, Alacrima, Short Stature, Dysmorphism, and Intellectual Disability

The alacrima, achalasia, and mental retardation syndrome (AAMR) is a newly described autosomal recessive disorder characterized by the onset of these 3 main features at birth or in early infancy. At present, only 16 cases have been reported. Recently, it was shown that AAMR is due to mutations in the guanosine diphosphate (GDP)-mannose pyrophosphorylase A (GMPPA) gene. These mutations induce a significant GDP-mannose overload, which may affect protein glycosylation. Herein, for the first time, we describe 2 adult sisters with AAMR with a previously not reported deleterious homozygous missense mutation c.1118G>C (p.Arg373Pro) in the GMPPA gene, born to healthy consanguineous heterozygous parents from an ancient endogamous population. The main symptoms in both sisters started soon after birth with achalasia and feeding difficulties, requiring surgical treatment. Both sisters showed alacrima identified during the first months of life, delayed psychomotor development, speech delay, facial dysmorphism, limb defects, short stature, and moderate intellectual disability. Alacrima and feeding difficulties due to achalasia during the neonatal period or first months of life, in the absence of adrenal cortical insufficiency, should spur to investigate AAMR by sequencing the GMPPA gene.

Heterogenous Distribution of MTHFR Gene Variants among Mestizos and Diverse Amerindian Groups from Mexico

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. Folate deficiency has been related to several conditions, including neural tube defects (NTDs) and cardiovascular diseases. Hence, MTHFR genetic variants have been studied worldwide, particularly the C677T and A1298C. We genotyped the C677T and A1298C MTHFR polymorphisms in Mexican Amerindians (MAs), from the largest sample included in a genetic study (n = 2026, from 62 ethnic groups), and in a geographically-matched Mexican Mestizo population (MEZ, n = 638). The 677T allele was most frequent in Mexican individuals, particularly in MAs. The frequency of this allele in both MAs and MEZs was clearly enriched in the South region of the country, followed by the Central East and South East regions. In contrast, the frequency of the 1298C risk allele in Mexicans was one of the lowest in the world. Both in MAs and MEZs the variants 677T and 1298C displayed opposite allele frequency gradients from southern to northern Mexico. Our findings suggest that in Mestizos the 677T allele was derived from Amerindians while the 1298C allele was a European contribution. Some subgroups showed an allele frequency distribution that highlighted their genetic diversity. Notably, the distribution of the frequency of the 677T allele was consistent with that of the high incidence of NTDs reported in MEZ.

Clinical and Genetic Findings in Mexican Patients with Duane Anomaly and Radial Ray Malformations/Okihiro Syndrome

BACKGROUND

Okihiro syndrome is an autosomal-dominant condition characterized by radial ray malformations associated with Duane anomaly and other clinical characteristics. SALL4 mutations have been identified in 80-90% of patients with Duane- Radial ray defects/Okihiro syndrome. We report the clinical findings and results of SALL4 sequencing from a group of Mexican patients with this disorder.

OBJECTIVE

Clinical description and identification of SALL4 mutations in Mexican subjects with radial defects and Duane anomaly.

MATERIALS AND METHODS

Five unrelated index cases were studied. Complete ophthalmologic and general physical examination was performed in all patients. Polymerase chain reaction amplification and automated nucleotide sequencing of coding exons and intron-exon junctions of SALL4 gene were carried out in genomic DNA.

RESULTS

A novel heterozygous deletion was identified in one patient. Intragenic heterozygous single nucleotide polymorphisms on SALL4 gene ruled out deletions of some exons in other affected patients in whom non-pathogenic variants were identified by Sanger sequencing. Likewise, multiplex ligation-dependent probe amplification analysis ruled out large deletions in this gene.

CONCLUSION

We observed a low frequency of SALL4 mutations in Mexican patients with clinical criteria of Okihiro syndrome.

Identification of Copy Number Variations in Isolated Tetralogy of Fallot

Tetralogy of Fallot (ToF) is one of the most common and severe congenital heart defects (CHD). Recently, unbalanced structural genomic variants or copy number variations (CNVs) were proposed to be involved in the etiology of many complex diseases, including CHDs. The aim of this study was to investigate the frequency of CNVs in a region with a high density of CNVs, 22q11.2, and other regions with CHD-related genes in a sample of 52 Mexican mestizo patients with isolated ToF and negative fluorescence in situ hybridization staining for 22q11. CNVs were studied using two multiplex ligation-dependent probe amplification (MLPA) kits, SALSA P250-B1® (DiGeorge gene region) and SALSA MLPA P311-A1® CHD-related gene regions (GATA4, NKX2-5, TBX5, BMP4, and CRELD1). The MLPA assay detected a de novo CNV deletion of the probes located in exons 2 and 7 of the TBX1 gene in one of the 52 patients studied; this result was confirmed by real-time quantitative polymerase chain reaction. This deletion was not present in the patient's parents and 104 chromosomes from healthy control subjects. Our results clearly suggest a possible etiologic association between the TBX1 deletion and the ToF in our patient.

Genetic Risk Determinants for Cigarette Smoking Dependence in Mexican Mestizo Families

INTRODUCTION

Tobacco smoking is a leading cause of mortality in developed and developing countries. Despite antitobacco and smoke-free policies, the prevalence of active smokers in Mexican urban populations has remained stable. Mexican smokers differ from Caucasian and other ethnic groups, probably due to sociocultural and genetic background characteristics. This study explored the effect of known genetic variants on smoking behavior in Mexico City residents.

METHODS

Three hundred sixty-four Mexican Mestizo Mexico City residents from 87 families with at least one smoker were assessed for association of 12 gene variants of six candidate genes (CHRNA4, CHRNB2, DRD2, ANKK1, SLC6A3, and CYP2A6) with cigarette consumption, age of initiation and smoking duration. The Family Based Association Test, an extension of the Transmission Disequilibrium Test, was used to perform family-based association analysis.

RESULTS

The Family Based Association Test showed statistically significant association between the rs2072658 polymorphism of the CHRNB2 gene and smoking-related phenotypes such as: smoking status (SS), age of onset (AO), years of smoking, and psychological dependence (PD) evaluated by the Glover-Nilsson Smoking Behavior Questionnaire. After Bonferroni correction, only the association with AO remained significant (P = .003). Statistically significant association was also observed for the CYP2A6 rs28399433 T allele with SS (P = .003) and PD (P = .003).

CONCLUSIONS

Our results indicate effects of the rs2072658 CHRNB2 and rs28399433 CYP2A6 gene variants on AO, SS and PD in Mexican Mestizo smokers. A mild effect of other analyzed gene variants, which may contribute to a putative polygenic predisposition for smoking, is suggested.

IMPLICATIONS

The understanding of genetic and environmental determinants in the Mexican population is important for other Latin American populations as well, living in their own countries or moving to other ones, particular due to the current migration characteristics and particular genetic background like the Mexican Mestizo and other Central American populations with similar characteristics and migrating to neighbor developed countries, introducing their own smoking behavior and contributing importantly to the genetic pool of the receptor country.

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis: variable phenotypic expression in three affected sisters from Mexican ancestry

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is a rare autosomal recessive renal disease caused by mutations in genes for the tight junction transmembrane proteins Claudin-16 (CLDN16) and Claudin-19 (CLDN19). We present the first case report of a Mexican family with three affected sisters carrying a p.Gly20Asp mutation in CLDN19 whose heterozygous mother showed evident hypercalciuria and normal low magnesemia without any other clinical, laboratory, and radiological symptoms of renal disease making of her an unsuitable donor. The affected sisters showed variable phenotypic expression including age of first symptoms, renal urinary tract infections, nephrolithiasis, nephrocalcinosis, and eye symptoms consisting in retinochoroiditis, strabismus, macular scars, bilateral anisocoria, and severe myopia and astigmatism. End stage renal disease due to renal failure needed kidney transplantation in the three of them. Interesting findings were a heterozygous mother with asymptomatic hypercalciuria warning on the need of carefully explore clinical, laboratory, kidney ultrasonograpy, and mutation status in first degree asymptomatic relatives to avoid inappropriate kidney donors; an evident variable phenotypic expression among patients; the identification of a mutation almost confined to Spanish cases and a 3.5 Mb block of genomic homozygosis strongly suggesting a common remote parental ancestor for the gene mutation reported.

Clinical, imaging, and molecular findings in a sample of Mexican families with pantothenate kinase-associated neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal recessive disorder characterized by iron accumulation in the brain, because of mutations in the PANK2 gene. Phenotypic and genotypic characteristics of 11 patients from five Mexican families with PKAN disease are reported. Sequencing of PANK2 confirmed the diagnosis. The 11 patients had dysarthria associated with dystonia and Parkinsonism in six. Brain magnetic resonance imaging (MRI) showed the 'eye-of-the-tiger' sign in all patients. Three different mutations were identified, a novel one (p.A469P) and two (p.G219V and p.N404I) very rare. Homozygous sibs for the p.G219V mutation had a severe disease progression with early death. Dystonia predominated in the p.A469P/p.N404I compound heterozygous patients. Homozygous for p.N404I showed Parkinsonism, tics and personality and speech disorders. Early and late disease onset and variable expression was present in carriers of the different identified mutations. The 'eye-of-the-tiger' is an excellent neuroimaging hallmark to predict PANK2 mutations. We detected a 'cluster' of patients harboring the p.N404I mutation, strongly suggesting a founder effect for this mutation. This is the first familial clinical-genetic PKAN disease study accomplished in Mexico.

[Congenital malformations in the offspring of epileptic mothers with and without anticonvulsant treatment]

OBJECTIVE

To determine the prevalence at birth and type of congenital malformations (CM) in newborns of epileptic mothers (NEM) treated and not treated with anticonvulsants, the correlation anticonvulsant/CM and other developmental disorders.

MATERIALS AND METHODS

Multicenter case-control study, in 166 live births NEM diagnosed in 21 501 newborns with CM and respective controls from the Registro y Vigilancia Epidemiológica de Malformaciones Congénitas (RYVEMCE).

RESULTS

The frequency of CM in NEM treated with anticonvulsants was higher (48.3%) than in NEM of untreated mothers (28.3%), (OR= 2.37 IC95% 1.08-5.40), p=0.03. CMs most frequently found were: spina bifida, limb reduction defects, cleft lip palate, microcephaly, anotia/microtia, hypospadias, polydactyly, cleft palate, anophthalmia/ microphthalmia and omphalocele. No differences among monotherapy and polytherapy were observed. Diphenyl-hydantoin, carbamazepine and valproic acid were the most frequently anticonvulsants used.

CONCLUSIONS

Our results show the teratogenicity of epilepsy by itself, the synergistic effect of some anticonvulsants, and the need of an appropriate periconceptional control of the disease and treatment.

Hormone therapy during pregnancy and isolated hypospadias: an international case-control study

Mothers of boys with hypospadias and control mothers were interviewed in eight malformation monitoring programs around the world. Hormone therapy was used quite frequently in five but rarely in three of the programs. The odds ratio for hypospadias after hormone therapy during pregnancy was 2.8 (95% confidence limits 1.2, 6.9) but there was no correlation between the timing of hormone therapy and the location of the urethral orifice, nor between the severity of the malformation and hormone therapy. Programs with the highest hormone exposure rate showed the lowest odds ratio for pregnancy bleeding, the most common reason for hormone therapy. These latter findings cast doubts on the causal association between hormone therapy and isolated hypospadias. Alternative explanations are recall or interviewer bias or unidentified confounders.

Prevalence of esophageal atresia among 18 international birth defects surveillance programs

BACKGROUND

The prevalence of esophageal atresia (EA) has been shown to vary across different geographical settings. Investigation of geographical differences may provide an insight into the underlying etiology of EA.

METHODS

The study population comprised infants diagnosed with EA during 1998 to 2007 from 18 of the 46 birth defects surveillance programs, members of the International Clearinghouse for Birth Defects Surveillance and Research. Total prevalence per 10,000 births for EA was defined as the total number of cases in live births, stillbirths, and elective termination of pregnancy for fetal anomaly (ETOPFA) divided by the total number of all births in the population.

RESULTS

Among the participating programs, a total of 2943 cases of EA were diagnosed with an average prevalence of 2.44 (95% confidence interval [CI], 2.35-2.53) per 10,000 births, ranging between 1.77 and 3.68 per 10,000 births. Of all infants diagnosed with EA, 2761 (93.8%) were live births, 82 (2.8%) stillbirths, 89 (3.0%) ETOPFA, and 11 (0.4%) had unknown outcomes. The majority of cases (2020, 68.6%), had a reported EA with fistula, 749 (25.5%) were without fistula, and 174 (5.9%) were registered with an unspecified code.

CONCLUSIONS

On average, EA affected 1 in 4099 births (95% CI, 1 in 3954-4251 births) with prevalence varying across different geographical settings, but relatively consistent over time and comparable between surveillance programs. Findings suggest that differences in the prevalence observed among programs are likely to be attributable to variability in population ethnic compositions or issues in reporting or registration procedures of EA, rather than a real risk occurrence difference. Birth Defects Research (Part A), 2012.

Phocomelia: a worldwide descriptive epidemiologic study in a large series of cases from the International Clearinghouse for Birth Defects Surveillance and Research, and overview of the literature

Epidemiologic data on phocomelia are scarce. This study presents an epidemiologic analysis of the largest series of phocomelia cases known to date. Data were provided by 19 birth defect surveillance programs, all members of the International Clearinghouse for Birth Defects Surveillance and Research. Depending on the program, data corresponded to a period from 1968 through 2006. A total of 22,740,933 live births, stillbirths and, for some programs, elective terminations of pregnancy for fetal anomaly (ETOPFA) were monitored. After a detailed review of clinical data, only true phocomelia cases were included. Descriptive data are presented and additional analyses compared isolated cases with those with multiple congenital anomalies (MCA), excluding syndromes. We also briefly compared congenital anomalies associated with nonsyndromic phocomelia with those presented with amelia, another rare severe congenital limb defect. A total of 141 phocomelia cases registered gave an overall total prevalence of 0.62 per 100,000 births (95% confidence interval: 0.52-0.73). Three programs (Australia Victoria, South America ECLAMC, Italy North East) had significantly different prevalence estimates. Most cases (53.2%) had isolated phocomelia, while 9.9% had syndromes. Most nonsyndromic cases were monomelic (55.9%), with an excess of left (64.9%) and upper limb (64.9%) involvement. Most nonsyndromic cases (66.9%) were live births; most isolated cases (57.9%) weighed more than 2,499 g; most MCA (60.7%) weighed less than 2,500 g, and were more likely stillbirths (30.8%) or ETOPFA (15.4%) than isolated cases. The most common associated defects were musculoskeletal, cardiac, and intestinal. Epidemiological differences between phocomelia and amelia highlighted possible differences in their causes.

Cyclopia: an epidemiologic study in a large dataset from the International Clearinghouse of Birth Defects Surveillance and Research

Cyclopia is characterized by the presence of a single eye, with varying degrees of doubling of the intrinsic ocular structures, located in the middle of the face. It is the severest facial expression of the holoprosencephaly (HPE) spectrum. This study describes the prevalence, associated malformations, and maternal characteristics among cases with cyclopia. Data originated in 20 Clearinghouse (ICBDSR) affiliated birth defect surveillance systems, reported according to a single pre-established protocol. A total of 257 infants with cyclopia were identified. Overall prevalence was 1 in 100,000 births (95%CI: 0.89-1.14), with only one program being out of range. Across sites, there was no correlation between cyclopia prevalence and number of births (r = 0.08; P = 0.75) or proportion of elective termination of pregnancy (r = -0.01; P = 0.97). The higher prevalence of cyclopia among older mothers (older than 34) was not statistically significant. The majority of cases were liveborn (122/200; 61%) and females predominated (male/total: 42%). A substantial proportion of cyclopias (31%) were caused by chromosomal anomalies, mainly trisomy 13. Another 31% of the cases of cyclopias were associated with defects not typically related to HPE, with more hydrocephalus, heterotaxia defects, neural tube defects, and preaxial reduction defects than the chromosomal group, suggesting the presence of ciliopathies or other unrecognized syndromes. Cyclopia is a very rare defect without much variability in prevalence by geographic location. The heterogeneous etiology with a high prevalence of chromosomal abnormalities, and female predominance in HPE, were confirmed, but no effect of increased maternal age or association with twinning was observed.

Conjoined twins: a worldwide collaborative epidemiological study of the International Clearinghouse for Birth Defects Surveillance and Research

Conjoined twins (CT) are a very rare developmental accident of uncertain etiology. Prevalence has been previously estimated to be 1 in 50,000 to 1 in 100,000 births. The process by which monozygotic twins do not fully separate but form CT is not well understood. The purpose of the present study was to analyze diverse epidemiological aspects of CT, including the different variables listed in the Introduction Section of this issue of the Journal. The study was made possible using the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) structure. This multicenter worldwide research includes the largest sample of CT ever studied. A total of 383 carefully reviewed sets of CT obtained from 26,138,837 births reported by 21 Clearinghouse Surveillance Programs (SP) were included in the analysis. Total prevalence was 1.47 per 100,000 births (95% CI: 1.32-1.62). Salient findings including an evident variation in prevalence among SPs: a marked variation in the type of pregnancy outcome, a similarity in the proportion of CT types among programs: a significant female predominance in CT: particularly of the thoracopagus type and a significant male predominance in parapagus and parasitic types: significant differences in prevalence by ethnicity and an apparent increasing prevalence trend in South American countries. No genetic, environmental or demographic significant associated factors were identified. Further work in epidemiology and molecular research is necessary to understand the etiology and pathogenesis involved in the development of this fascinating phenomenon of nature.

Amelia: a multi-center descriptive epidemiologic study in a large dataset from the International Clearinghouse for Birth Defects Surveillance and Research, and overview of the literature

This study describes the epidemiology of congenital amelia (absence of limb/s), using the largest series of cases known to date. Data were gathered by 20 surveillance programs on congenital anomalies, all International Clearinghouse for Birth Defects Surveillance and Research members, from all continents but Africa, from 1968 to 2006, depending on the program. Reported clinical information on cases was thoroughly reviewed to identify those strictly meeting the definition of amelia. Those with amniotic bands or limb-body wall complex were excluded. The primary epidemiological analyses focused on isolated cases and those with multiple congenital anomalies (MCA). A total of 326 amelia cases were ascertained among 23,110,591 live births, stillbirths and (for some programs) elective terminations of pregnancy for fetal anomalies. The overall total prevalence was 1.41 per 100,000 (95% confidence interval: 1.26-1.57). Only China Beijing and Mexico RYVEMCE had total prevalences, which were significantly higher than this overall total prevalence. Some under-registration could influence the total prevalence in some programs. Liveborn cases represented 54.6% of total. Among monomelic cases (representing 65.2% of nonsyndromic amelia cases), both sides were equally involved, and the upper limbs (53.9%) were slightly more frequently affected. One of the most interesting findings was a higher prevalence of amelia among offspring of mothers younger than 20 years. Sixty-nine percent of the cases had MCA or syndromes. The most frequent defects associated with amelia were other types of musculoskeletal defects, intestinal, some renal and genital defects, oral clefts, defects of cardiac septa, and anencephaly.

Cloacal exstrophy: an epidemiologic study from the International Clearinghouse for Birth Defects Surveillance and Research

Cloacal exstrophy presents as a complex abdominal wall defect thought to result from a mesodermal abnormality. Anatomically, its main components are Omphalocele, bladder Exstrophy and Imperforate anus. Other associated malformations include renal malformations and Spine defects (OEIS complex). Historically, the prevalence ranges from 1 in 200,000 to 400,000 births, with higher rates in females. Cloacal exstrophy is likely etiologically heterogeneous as suggested by its recurrence in families and occurrence in monozygotic twins. The defect has been described in infants with limb-body wall, with trisomy 18, and in one pregnancy exposed to Dilantin and diazepam. Due to its rarity, the use of a nonspecific diagnostic code for case identification, and lack of validation of the clinical findings, cloacal exstrophy remains an epidemiologic challenge. The purpose of this study was to describe the prevalence, associated anomalies and maternal characteristics among infants born with cloacal exstrophy. We used data from the International Clearinghouse for Birth Defects Surveillance and Research submitted from 18 birth defect surveillance programs representing 24 countries. Cases were clinically evaluated locally and reviewed centrally by two authors. Cases of persistent cloaca were excluded. A total of 186 cases of cloacal exstrophy were identified. Overall prevalence was 1 in 131,579 births: ranging from 1 in 44,444 births in Wales to 1 in 269,464 births in South America. Live birth prevalence was 1 in 184,195 births. Prevalence ratios did not vary by maternal age. Forty-two (22.6%) cases met the criteria for the OEIS complex, whereas 60 (32.3%) were classified as OEI and 18 (9.7%) as EIS (one with suspected VATER (0.5%)). Other findings included two cases with trisomy 13 (one without a karyotype confirmation), one with mosaic trisomy 12 (0.5%), one with mosaic 45,X (0.5%) and one classified as having amnion band sequence (0.5%). Twenty-seven (14.5%) infants had other anomalies unrelated to cloacal exstrophy. Cloacal exstrophy is a rare anomaly with variability in prevalence by geographic location. The proportion of cases classified as OEIS complex was lower in this study than previously reported. Among all cases, 54.8% were reported to have an omphalocele.

Bladder exstrophy: an epidemiologic study from the International Clearinghouse for Birth Defects Surveillance and Research, and an overview of the literature

Bladder exstrophy (BE) is a complex congenital anomaly characterized by a defect in the closure of the lower abdominal wall and bladder. We aimed to provide an overview of the literature and conduct an epidemiologic study to describe the prevalence, and maternal and case characteristics of BE. We used data from 22 participating member programs of the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR). All cases were reviewed and classified as isolated, syndrome, and multiple congenital anomalies. We estimated the total prevalence of BE and calculated the frequency and odds ratios for various maternal and case characteristics. A total of 546 cases with BE were identified among 26,355,094 births. The total prevalence of BE was 2.07 per 100,000 births (95% CI: 1.90-2.25) and varied between 0.52 and 4.63 among surveillance programs participating in the study. BE was nearly twice as common among male as among female cases. The proportion of isolated cases was 71%. Prevalence appeared to increase with increasing categories of maternal age, particularly among isolated cases. The total prevalence of BE showed some variations by geographical region, which is most likely attributable to differences in registration of cases. The higher total prevalence among male cases and older mothers, especially among isolated cases, warrants further attention.

How valid are the rates of Down syndrome internationally? Findings from the International Clearinghouse for Birth Defects Surveillance and Research

Rates of Down syndrome (DS) show considerable international variation, but a systematic assessment of this variation is lacking. The goal of this study was to develop and test a method to assess the validity of DS rates in surveillance programs, as an indicator of quality of ascertainment. The proposed method compares the observed number of cases with DS (livebirths plus elective pregnancy terminations, adjusted for spontaneous fetal losses that would have occurred if the pregnancy had been allowed to continue) in each single year of maternal age, with the expected number of cases based on the best-published data on rates by year of maternal age. To test this method we used data from birth years 2000 to 2005 from 32 surveillance programs of the International Clearinghouse for Birth Defects Surveillance and Research. We computed the adjusted observed versus expected ratio (aOE) of DS birth prevalence among women 25-44 years old. The aOE ratio was close to unity in 13 programs (the 95% confidence interval included 1), above 1 in 2 programs and below 1 in 18 programs (P < 0.05). These findings suggest that DS rates internationally can be evaluated simply and systematically, and underscores how adjusting for spontaneous fetal loss is crucial and feasible. The aOE ratio can help better interpret and compare the reported rates, measure the degree of under- or over-registration, and promote quality improvement in surveillance programs that will ultimately provide better data for research, service planning, and public health programs.

[Diabetes, pregnancy and birth defects]

BACKGROUND

Diabetes mellitus affects 3 to 10% of pregnant women. The reported frequency of congenital malformations (CM) in diabetic mothers is 5.5 to 10%, contributing these defects to approximately 40% of the neonatal mortality in children of diabetic mothers (CDM).

OBJECTIVE

To investigate the frequency and type of congenital malformations in a sample of livebirths of diabetic mothers from the Mexican population.

MATERIAL AND METHODS

The analyzed information was obtained from the RYVEMCE (Registro y Vigilancia Epidemiológica de Malformaciones Congénitas). We analysed the type and frequency of the different CM diagnosed. These frequencies were compared with the whole amount of those CM included in the database of our registry (20,381). As part of the analysis, other maternal and neonatal variables were also compared between CDM and the control group.

RESULTS

A total of 314 CDM (0.77%), 234 malformed and 80 non malformed were identified. The frequencies of cleft palate (CP), limb reduction defect (LRD) and microcephaly (MIC) were significantly higher in CDM than in the rest of malformed newborns of not diabetic mothers of the RYVEMCE (OR: 9.9, 3.8 and 10.0, respectively). A higher frequency of macrosomia was observed in CDM (18.0%) than in controls (6.1%), OR: 3.4, p < 0.001, in the frequency of preterm birth (28.5% than controls 13.0%), OR: 3.02, p < 0.0001 and in caesarean delivery (71.5% than controls 44.4%) OR: 3.15, p < 0.00001.

CONCLUSIONS

Our results confirm the higher frequency of CM in CDM and in particular a higher risk for CP, LRD and MIC. Pregnancy and delivery complications such as macrosomia and preterm and caesarean delivery were also more frequent in CDM that controls. Certain associations of CM not described previously, were observed in the studied sample. Our results confirm the need of pregnancy planning including a pre-gestational and gestational control of maternal glycaemia, particularly in a population with such a high prevalence of diabetes mellitus as the observed in the Mexican one.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) in two Mexican brothers harboring a novel mutation in the ECGF1 gene

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disease caused by mutations in the thymidine phosphorylase gene located on chromosome 22q13.32-ter, causing defective functioning of the enzyme. At present 87 sporadic or familial cases have been reported and 52 different mutations identified. We present herein the clinical, neuromuscular and molecular findings of two affected brothers from an indigenous Mexican family living in a very small village not far from Mexico City, both brothers being homozygous for a novel mutation (Leu133Pro) in exon 3 of the ECGF1 gene.

Environmental influence on the worldwide prevalence of a 776C->G variant in the transcobalamin gene (TCN2)

BACKGROUND

A 776C-->G variant (dbSNP ID: rs1801198) in the transcobalamin gene (TCN2; MIM# 275350) decreases the cellular and plasma concentration of transcobalamin and thereby influences the cellular availability of vitamin B(12).

OBJECTIVE

To evaluate the worldwide prevalence of this variant and its association with homocysteine plasma level.

METHODS

The study was performed in 1433 apparently healthy subjects, including Afro-Americans and Afro-Africans and in 251 Afro-Africans participants with severe malaria.

RESULTS

The frequencies of the 776G allele were the highest in China (0.607; 95% CI 0.554 to 0.659), low in West Africa (Bénin and Togo, 0.178; 0.154 to 0.206), and intermediate in France (0.445; 0.408 to 0.481), Italy (0.352; 0.299 to 0.409), Morocco (0.370; 0.300 to 0.447) and Mexico (0.374; 0.392 to 0.419). The 776G genotype was more frequent in Afro-Americans from New York (16.7; 8.4 to 30.7) and in Afro-African patients with severe malaria (6.0%; 95% CI 3.7 to 9.6) than in healthy Afro-African volunteers (p = 0.0004 and p = 0.033, respectively), while no difference was observed for MTHFR 677TT and 677T alleles. A disequilibrium of TCN2 genotype distribution was recorded in patients with severe malaria, with a twofold higher GG genotype than expected (p = 0.010). An association between the TCN2 polymorphism and homocysteine was observed only in Mexico and France, the two countries with the highest rate of low plasma concentration of vitamin B(12) (<100 pmol/l).

CONCLUSION

Given the dramatic heterogeneity of the 776G allele frequency worldwide, this polymorphism may be prone to a selective pressure or confers an evolutionary advantage in confronting environmental factors, one of which is malaria.

The role of the X chromosome in immunity and autoimmunity

Primary immunodeficiencies as well as autoimmune diseases have been associated to X chromosome abnormalities. Furthermore, the functional biology of the X chromosome is unique because genes located in this chromosome can undergo inactivation, and subsequently transcriptional silencing. Non-random X chromosome inactivation has been hypothesized to be involved in the development of autoimmunity. Recently X chromosome monosomy has also been proposed as a common etiologic mechanism for some autoimmune diseases. Herein, we review some of these findings above mentioned.

Prevalence of methylenetetrahydrofolate reductase 677T and 1298C alleles and folate status: a comparative study in Mexican, West African, and European populations

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism is heterogeneously distributed worldwide, with the highest and lowest frequencies of the T allele in Mexico and Africa, respectively, and a south-to-north gradient in Europe. Distribution of MTHFR 1298A-->C is less well known. It has been hypothesized that 677T frequency could result in part from gene-nutrient interactions.

OBJECTIVE

The objective was to compare the association of 677T and 1298C alleles with plasma concentrations of homocysteine, folate, and vitamin B-12 in geographical areas with contrasting 677T allele frequencies.

DESIGN

Healthy young adults (n = 1277) were recruited in Mexico City, the West African countries of Bénin and Togo, France, and Sicily (Italy). Homocysteine, folate, and vitamin B-12 were measured in plasma, and MTHFR polymorphisms were measured in genomic DNA.

RESULTS

Mexico City and Sicily reported the highest and Bénin and Togo reported the lowest plasma concentrations of folate. Mexico City had the highest 677T allele prevalence and the lowest influence of 677TT genotype on homocysteine, whereas the opposite was observed in Africa. The prevalence of the 1298C allele was lowest in the Mexicans and Africans and highest in the French. The percentage of the 677T genotype was significantly associated with the folate concentrations in 677CC carriers in a univariate analysis (R = 0.976; 95% CI: 0.797, 0.996; P < 0.0002) and in a multiple regression model that included homocysteine, vitamin B-12, and age (P = 0.0002).

CONCLUSION

Our data agree with the hypothesis of a gene-nutrient interaction between MTHFR 677C-->T polymorphism and folate status that may confer a selective advantage of TT-homozygous genotype when dietary intake of folate is adequate, at least in the areas studied.

Sex and congenital malformations: an international perspective

The study evaluated the sex distribution of major isolated malformations and common trisomies among a large and geographically varied sample. Eighteen registries from 24 countries contributed cases, which were centrally reviewed and classified in three clinical types as isolated, associated, or syndromic. We selected cases of 26 major defects (n = 108,534); trisomy 21, 18, and 13 (n = 30,114); other syndromes (n = 2,898); and multiple congenital anomalies (n = 24,197), for a total of 165,743 cases. We observed a significant deviation of sex distribution (compared to a sex ratio of 1.06 or male proportion of 51.4%) for 24 of the 29 groups (a male excess in 16, a female excess in 8), and in 8 of such groups these estimates varied significantly across registries. A male excess was noted for two left obstructive cardiac defects (hypoplastic left heart and coarctation of the aorta) and a female excess for all the main types of neural tube defects. A male excess was seen for omphalocele but not gastroschisis. For neural tube defects the female excess tended to be stronger in areas with historically high prevalence for these defects. For 15 of the 26 birth defects the sex distribution differed among isolated, associated, and syndromic cases. Some of these epidemiologic commonalities are consistent with known or putative developmental processes. Further, the geographic variation for some defects may reflect local prevalence rates and risk factors. Finally, the findings underscore the need for clinical classification (e.g., into isolated, multiple, syndromes) in studies of birth defects.

Isolated ectrodactyly caused by a heterozygous missense mutation in the transactivation domain of TP63

We report a Mexican boy with isolated ectrodactyly (split hand malformation) in whom a new mutation was identified in exon 3 of the TP63 gene. In contrast to previously reported patients with isolated split hand/foot anomaly and mutations in the DNA binding domain of Tp63, the mutation described herein induce an amino acid substitution (R97C) in the canonical transactivation (TA) domain. To our knowledge, this is the first naturally occurring mutation described so far in this part of the protein. Based on the genotype-phenotype correlation observed in our patient, we hypothesize that integrity of the TA domain of Tp63 is critical for normal limb development.

A rare case of gonadal agenesis with paramesonephric derivatives in a patient with a normal female karyotype

OBJECTIVE

To report a rare case of gonadal agenesis with rudimentary paramesonephric ducts derivatives in a female with a 46,XX normal karyotype.

DESIGN

Case study.

SETTING

National Institute of Health.

PATIENT(S)

An 18-year-old female with primary amenorrhea and lack of secondary sexual development.

INTERVENTION(S)

Clinical, gynecological, endocrine, and genetic evaluation. Laboratory studies conducted included measurement of pituitary, ovary, and thyroid hormones; analyses of G-banded chromosomes in peripheral blood and fibroblast cultures; search for genomic Y-chromosome DNA by fluorescence in situ hybridization and molecular biology techniques; X-ray, ultrasonography, echocardiographic and laparoscopic studies for the assessment of bone age, and genitourinary and other associated malformations.

MAIN OUTCOME MEASURE(S)

Clinical, hormonal, anatomical, and genetic characteristics of the patient.

RESULT(S)

The studies performed confirmed a prepubertal female with hypergonadotrophic hypogonadism, bilateral gonadal agenesis, a rudimentary uterus and fallopian tubes, a normal vagina, kidney, and urinary tract structures, and a 46,XX normal karyotype. The search for centromeric Y-chromosome DNA and SRY and ZFY genes was negative.

CONCLUSION(S)

A primary deficiency confined to the gonadal blastema and the nearby coelomic epithelium is proposed as an alternative embryologic mechanism to explain the occurrence of this singular sexual developmental defect.