The family members of the HD patients have to cope with the knowledge that the patient will suffer from mental and physical deterioration while accepting the fact that the HD patients’ children are at risk of getting the disease. The risk of developing HD in an offspring of an affected parent is 50%. One such case of full-term pregnancy is reported. It merits attention because of rarity of HD and lack of reports on it from Central India. Therefore, a careful study of family history is indispensable in the assessment and understanding of HD as it enables the prediction to be made for the fetus during pregnancy in 90% of cases. The case report also emphasizes the need of detecting DNA polymorphism by chorion biopsy or amniocentesis to avoid transmission of HD gene to further generations despite of ethical issues, which may be raised.
A Case Report
A 35-year-old Indian woman with history of amenorrhea or absence of menstruation of 9 months and labor pains was admitted in private hospital. Her pulse was 80 per min, blood pressure 110/80 mm Hg she had no edema. The abdomen examination showed height of uterus to be 36 weeks, tense, tender with moderate uterine contractions. Fetal heart was recorded to be normal. She had characteristic involuntary choric movements. The diagnosis of HD was established due to presence of chorea and history of progressive dementia and emotional disturbance supported by a positive family history. Her paternal grandmother suffered and died of the same symptoms. The grandmother had one daughter and four sons, of which the daughter and one son have no symptoms whereas three sons suffered. The age of onset of the patient’s father was at the age of 38 years and death occurred 12 years after onset. In the second son, onset was at the age of 35 years and he committed suicide after suffering for 10 years. The third son is 40 years of age and still alive but with same symptoms. The patient has three brothers and one sister all less than thirty years of age without any symptoms. The onset of symptoms in the patient was at the age of 30 years. She has three daughters, 17 years and 15 years and a son 13 years old. She delivered normally a healthy male child. The postpartum period was uneventful. The doctors succeeded in convincing her husband to undergo vasectomy.
As the case denotes, normal pregnancy and delivery is possible in a patient suffering from HD. As the offspring are at a 50% risk of inheriting the disease, prediction of this risk is essential. The identification of a deoxyribonucleic acid (DNA) sequence G-8 on chromosome 4 showed close genetic linkage to HD. Over the years availability of new DNA markers more tightly linked to the HD locus than the G-8 probes has improved predictive accuracy for both pre-symptomatic and prenatal exclusion testing. Prenatal exclusion testing can be an ideal option for high-risk individuals wishing to procreate as HD trait shows vertical transmission through successive generations. Non-availability of such predictive tests in India and the added economic restrain are the limitations. According to a study by Harper on Genetic Testing and Family Structure shows that only when a specific test for the HD gene itself is available it may be feasible to make a prediction for an isolated subject without studying the family unit. Meanwhile families are likely to benefit from prediction along family structures. In conclusion, pre symptomatic and prenatal exclusion testing by genetic counseling definitively predicts the risk of HD. But the family structure will remain crucial for prediction, as the identification of HD gene in Central India seems to be some way away.
Here are some of the resources for genetic counseling in India:
- Genetic And Mental Retardation Clinic
of Paediatrics, AIIMS, New Delhi-110029
Phone number: 26588500
- Surendra genetics Laboratory, Lloyd’s road, Royapettah, Chennai,India
- Genetics department, Manipal Hospital, Karnataka.
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Wasmuth, John J., Jeffrey Hewitt, Barbara Smith, Denis Allard, Jonathan L. Haines, Douglas Skarecky, Eric Partlow, and Michael R. Hayden. “A Highly Polymorphic Locus Very Tightly Linked to the Huntington’s Disease Gene.” Nature 332.6166 (1988): 734-36. Web.