Triplet repeat polymorphism & fragile X syndrome in the Indian context.

Mental retardation due to fragile X syndrome is one of the genetic disorders caused by triplet repeat expansion. CGG repeat involved in this disease is known to exhibit polymorphism even among normal individuals. Here we describe the development of suitable probes for detection of polymorphism in CGG repeat at FMR1 locus as well as the diagnosis of fragile X syndrome. Using these methods polymorphism at the FMR1 locus has been examined in 161 individuals. Ninety eight patients with unclassified mental retardation were examined, of whom 7 were found to have the expanded (CGG) allele at the FMR1 locus. The hybridization pattern for two patients has been presented as representative data.

The etiologic patterns in microcephaly with mental retardation.

Microcephaly with mental retardation forms a distinct subgroup among mentally retarded individuals. The paucity of studies on the etiology of this condition in India made the investigators to study this population. It HTO aimed to study the demographic and clinical characteristics, and the etiologic pattern in children with microcepltaly and mental retardation The sample consisted of 82 children who were examined by detailed clinical assessment and a battery of investigations. A definite etiology could be found in 56% of children which have been grouped into prenatal embryonic, prenatal maternal/environmental, and birth and neonatal causes. Non-genetic causes were the most common. The prenatal etiology constituted nearly twice that of birth and neonatal causes. Majority of the etiologic factors were preventable. The role of socio-environmental factors has been discussed As a group, the neurological disorders were found to be the most commonly associated medical condition. Malnutrition, specially of severe degree, was significantly associated with this group compared to the general population. The study findings indicate that there is a significant place for prevention.