Manovikas Biomedical Research & Diagnostic Centre, Kolkata 700 107, India.
Indian J Med Res. 2009 Dec;130(6):714-9.
BACKGROUND & OBJECTIVE: Screening for Fragile X syndrome (FRAXA), the most common genetic cause for mental retardation (MR), has mostly been carried out among MR patients. The present study was conducted to find out prevalence of FRAXA amongst children residing in the rural areas of West Bengal.
Demographic details including age, sex, nutritional status as well as birth, medical, and developmental histories, were collected amongst rural children (n=38,803) of West Bengal, India, over three years (2004-2007). Based on the records of scholastic backwardness, 179 children were short-listed and examined by a team of experts comprising of child psychiatrist, clinical psychologist, paediatrician and special educator. Blood samples were collected and molecular and cytogenetic studies were performed for identification of CGG repeats and determination of FMR1 gene promoter methylation.
Of the selected 179 children, six were diagnosed as Down syndrome, one as cerebral palsy and 140 as non-syndromic MR. These 140 children with MR were grouped as mild (56), moderate (60), and severely (4) retarded based on IQ; children <5 yr were grouped as developmental delay (20). FRAXA was not detected in any of these children (frequency being 0% with 0-.02% confidence interval). Prevalence of MR was found to be low (about 4/1000 children). Down syndrome also had a lower frequency (0.15/1000 children).
INTERPRETATION & CONCLUSION: The data obtained in the present study indicated that familial disorders like FRAXA were less frequent in the studied population.
脆性 X 综合征（FRAXA）是最常见的智力低下（MR）遗传病因，其筛查主要在 MR 患者中进行。本研究旨在了解西孟加拉邦农村地区儿童中 FRAXA 的患病率。
在三年内（2004-2007 年），收集了印度西孟加拉邦农村儿童（n=38803）的人口统计学详细信息，包括年龄、性别、营养状况以及出生、医疗和发育史。根据学业落后的记录，从 179 名儿童中选出并由一个由儿童精神病学家、临床心理学家、儿科医生和特殊教育工作者组成的专家组进行检查。采集血样，进行分子和细胞遗传学研究，以确定 CGG 重复序列并确定 FMR1 基因启动子甲基化。
在所选择的 179 名儿童中，有 6 名被诊断为唐氏综合征，1 名被诊断为脑瘫，140 名被诊断为非综合征性 MR。这 140 名智力低下的儿童根据智商分为轻度（56）、中度（60）和重度（4）迟钝；<5 岁的儿童分为发育迟缓（20）。在这些儿童中均未发现 FRAXA（频率为 0%，置信区间为 0-0.02%）。MR 的患病率较低（约为每 1000 名儿童中有 4 例）。唐氏综合征的频率也较低（每 1000 名儿童中有 0.15 例）。
本研究获得的数据表明，在研究人群中，家族性疾病如 FRAXA 较为少见。
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