Case Report

By Mr. Mohammed Furqan Khan , Ms. Prakruti Singh , Ms. Sarisha Kotlikar , Dr. Santosh Karmarkar , Dr. Rajeev Redkar , Dr. Manjari S Mukherjee
Corresponding Author Dr. Manjari S Mukherjee
Department of Medical Research, Cumballa Hill Hospital and Heart Institute, - India 400036
Submitting Author Dr. Manjari S Mukherjee
Other Authors Mr. Mohammed Furqan Khan
Institute of Chemical Technology, Department of Food Engineering , Nathala Parekh Marg, Matunga, Mumbai, India - India 400019

Ms. Prakruti Singh
Institute of Chemical Technology, Department of Food Engineering , Nathalal Parekh Marg, Matunga, Mumbai - India 400019

Ms. Sarisha Kotlikar
Institue of Chemical Technology, Department of Food Engineering , Nathalal Parekh Marg, Matunga, Mumbai - India 400019

Dr. Santosh Karmarkar
Spina Bifida Clinics, Pediatric Surgery, Mumbai - India 400050

Dr. Rajeev Redkar
Bai Jerbai Wadia Hospital for Children, Department of Pediatrics, Parel, Mumbai - India 400012


Neural tube defect, Down syndrome, Maternal DNA polymorphisms, Folate metabolism pathway

Khan M, Singh P, Kotlikar S, Karmarkar S, Redkar R, Mukherjee MS. Common Gene Polymorphisms in the Mother of a Child Born with Neural Tube Defect and Down Syndrome. WebmedCentral HUMAN GENETICS 2010;1(9):WMC00651
doi: 10.9754/journal.wmc.2010.00651
Submitted on: 23 Sep 2010 09:57:36 AM GMT
Published on: 23 Sep 2010 04:32:47 PM GMT


The purpose of this communication is to report an unusual case of an infant affected with both neural tube defect (NTD) and Down syndrome (DS). Genetic risk factors in the mother were investigated. As impaired folate metabolism is implicated in the etiology of NTD and DS, folate gene polymorphisms were determined in the case-mother. These included methylene tetrahydrofolate reductase gene (MTHFR) 677C>T, methionine synthase gene (MTR) 2756A>G, betaine homocysteine methyl transferase gene (BHMT) 742G>A, thymidylate synthase gene enhancer region (TSER) – 3 or 2 tandem repeats of 28-bp and TS gene, 6-bp deletion in 3’ untranslated region. The genotype distribution and minor allele frequencies were also determined in a group of female control subjects. The genotypes of case-mother was MTHFR 677CT, MTR 2756AG, TSER 3R2R, TS D0D6 and BHMT 742AA. The BHMT 742AA genotype, in combination of genotypes of case-mother at five, four or three polymorphic loci, was either absent or present in a small number of control women. The case mother was a life-long vegetarian. Although the precise maternal risk factor(s) cannot be pin-pointed, it is possible that BHMT 742AA genotype coupled with restricted intake of those folate micronutrients present chiefly in foods of animal origin may play a role.


The worldwide prevalence of neural tube defects (NTD) is estimated to be 300,000 to 400,000 live births annually with geographical variations such as about 1 in 1000 in the United States [1,2] and averagely about 3.63 per 1000 in India [3,4]. The prevalence of Down syndrome (DS) is estimated to be about 1:800 1:1000 live births annually [5, 6].  The major affliction of DS-affected children is the presence of moderate to severe mental retardation. Neural tube defects are a range of congenital malformations associated with the failure of the neural tube to close properly during early embryonic development leading to severe physical disability or death of the newborn. Clinical research evidence suggests that abnormal folate metabolism with impaired biological methylation that regulates gene expression may constitute maternal risk factors for NTD or DS [7, 8].  Due to this possible common etiology involved in the two birth disorders, investigations were carried out to explore any familial link between NTD and DS. A study in two series of families from separate countries, one with a family history of NTD and the other with history of DS demonstrated familial link between the two birth disorders [9]. However, this was not replicated in another study [10]. More uncommon than the occurrence of NTD and DS in the same family is their occurrence in the same individual. To the best of our information one case of a male child affected with both NTD and DS has been reported so far [11]. We report in this communication another case of a child affected with NTD and DS. In the reported case, the mother and the child had abnormal levels of folate metabolites and DNA hypomethylation in lymphocytes [11].  In the present communication we report common polymorphisms in genes encoding enzymes of the folate-dependent and independent pathways in the mother of the affected female child.

Subjects and Methods

The case was the second born female child of biologically unrelated parents of Asian Indian origin belonging to North India. Her condition was diagnosed by one of us (SJK) at his Pediatric Surgery unit in Ishayu Pediatric Specialty Clinic, Mumbai. The mother was 39 years old at childbirth, two years before her inclusion in the study. The infant was delivered full term by Caesarian section. Ultrasound of the spine revealed a tethered cord and a lumbar myelomengocoele with cauda equina roots in the thecal sac, diagnostic of NTD. Chromosomal analysis of peripheral blood lymphocytes stimulated with phytohaemagglutinin revealed trisomy of chromosome 21. The karyotype was diagnostic of DS. The 9-year older sibling of the case was a normal female child.
The mother was a hypertensive patient since her second pregnancy that ended in miscarriage. She was on medication with alpha-methyl dopa throughout her third pregnancy that ended in the birth of the affected offspring. Presently the mother is on medication with calcium channel antagonist namely amlodipine, besides calcium and iron supplements. After being explained the purpose of the study, she gave her written informed consent to participate. A sample of blood was withdrawn from the ante-cubital vein with minimum stasis. Genomic DNA was extracted from peripheral blood leucocytes for documenting DNA polymorphisms.
The DNA polymorphisms that were determined in the mother by previously described methods were as follows: i) methylene tetrahydrofolate reductase gene (MTHFR) 677C>T [12]; ii) methionine synthase gene (MTR) 2759A>G [13]; iii) betaine homocysteine methyl transferase gene (BHMT)742G>A [14]; iv) thymidylate synthase gene enhancer region (TSER) – three or two copies of 28-bp tandem repeats [15]; and v) TS gene, 6-bp deletion in 3’ untranslated region (UTR) [16]. The genotype and minor allele frequencies at these loci were determined in a sample of female subjects enrolled in a previous study, to compare the combined genotype of the case mother with this group. The details of enrolment are described elsewhere [17]. Briefly, this group consisted of 114 females, 57 with angiographically diagnosed coronary artery disease (CAD) and 57 age-matched asymptomatic controls from the general population [17]. None of the women with CAD had history of children born with NTD or DS as documented in the hospital case records. In case of control women this information was not available.

Results and Discussion

The body mass index of the case-mother computed from her height and weight measurements was 25.5 Kg/M2. She reported being a life long vegetarian. Vegetarianism spanned across generations in her family. Her daily intake of butter, ghee (clarified butter) and vegetable oils were in the first, second and third quintiles respectively of daily intake of the control group of women. She may probably have a restricted dietary intake of choline that is present more in animal than in vegetable fats. Choline is a precursor of betaine, the substrate of BHMT enzyme. Her daily intake of vitamin B12 (present mainly in foods of animal origin) assessed from standard 24-hour recall and food frequency questionnaire was 0.69 µg, well below the recommended daily allowance of 2.4 µg [18]. The case-mother was found to have a single copy of variant allele (heterozygous) for MTHFR 677C>T and MTR 2756A>G single nucleotide polymorphisms (SNPs), TSER repeat polymorphism and TS 6-bp deletion polymorphism, but two copies of the variant allele (homozygous variant) for BHMT 742G>A SNP. The genotype distribution and minor allele frequencies of these polymorphisms in the female population is given in Table 1. The number of female control subjects with the same combination of genotypes at multiple loci as in the case-mother was counted (Table 2). Unlike in the case-mother, the BHMT 742AA genotype was either absent or present in a small number of control women in combination of genotypes at five, four or three polymorphic loci (Table 2).
It is difficult to identify maternal risk factor(s) for NTD and DS-affected offspring in the present case. Although the variant allele frequency of the BHMT 742G>A SNP was present in 25% and BHMT 742AA genotype in 6% of the female controls (Table 1), the 742AA genotype in combination with other folate genotypes at three, four or five loci in the case-mother was present in none (0/110) to 2.7% (3/110) of the controls (Table 2). This may suggest that among folate gene polymorphisms documented, BHMT 742AA genotype is likely to be associated with increased risk for the case born with NTD and DS. Although the effect of ‘A’ allele on BHMT activity is not established, one study suggested an increased maternal risk for NTD in its presence [19]. Dietary deficiency of choline was reported to increase the maternal risk of having a baby with NTD [20]. A life-long vegetarian diet of the case-mother with a low intake of vitamin B12 – dietary co-factor of MTR of folate-dependent pathway of remethylation of homocysteine, and a presumed restricted intake of choline with possible altered BHMT activity due to the presence of SNP in two copies may impact upon the folate-independent pathway. It may be speculated that these could compromise remethylation of homocysteine and impair biological methylation thereby enhancing maternal risk for NTD and DS.


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Source(s) of Funding

The study was supported by an institutional grant (ICT, Mumbai) from World Bank’s Technical Quality Improvement Program (TEQIP) ‘Service to Society’ scheme and Baun Foundation Trust (BFT), Mumbai at Cumballa Hill Hospital and Heart Institute. BFT supported PRS.

Competing Interests

None to declare


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