Detection of inherited metabolic diseases in children with mental handicap

Mental Retardation is a condition where complex interactions of intrinsic and extrinsic factors hamper mental and sometimes physical growth of the child during developmental period. This study was carried out to detect cause of Mental Retardation in 2000 cases of developmental delay by a multidisciplinary team comprising of a Pediatrician, Cytogeneticist, Biochemist, Psychologist and Speech and Occupational therapists. The causes for developmental delay are broadly divided into Genetic, Environmental and Idiopathic (no specific cause found) factors. The complete diagnosis was possible in 1192(60%) cases. Genetic factors were found in 477(23.8%) cases and environmental factors covered 692(34.6%) cases as a cause of retardation. The most common genetic cause is chromosomal abnormalities which were found in 355 (17.75%) cases. Another major group comprising of 122 (6.1%) cases was that of the disorders which follow Mendelian inheritance. Autosomal recessive conditions, which covers majority of metabolic disorders, are detected in 48(2.4%) cases. During this screening the most common inherited metabolic condition detected is Mucopolysaccharidosis, a Lysosomal Storage Disorder followed by Amino acid abnormalities like Phenylketonuria, Alkaptonuria and Tyrosinuria.