Burden of genetic disorders in India.

India, like other developing countries, is facing an accelerating demographic switch to non-communicable diseases. In the cities congenital malformations and genetic disorders are important causes of morbidity and mortality. Due to the high birth rate in India a very large number of infants with genetic disorders are born every year almost half a million with malformations and 21,000 with Down syndrome. In a multi-centric study on the causes of referral for genetic counselling the top four disorders were repeated abortions (12.4%), identifiable syndromes (12.1%), chromosomal disorders (11.3%) and mental retardation (11%). In a more recent study in a private hospital the top reasons for referral were reproductive genetics (38.9%)--comprising prenatal diagnosis, recurrent abortions, infertility and Torch infections--mental retardation +/- multiple congenital anomalies (16.1%), Down syndrome (9.1%), thalassemia/haemophilia (8.8%), and muscle dystrophy/spinal muscular atrophy (8.4%). The disorders for which prenatal has been done over an 18-month-period are given. A recent study carried out in three centers (Mumbai, Delhi and Baroda) on 94,610 newborns by using a uniform proforma showed a malformation frequency of 2.03%, the commonest malformations are neural tube defects and musculo-skeletal disorders. The frequency of Down syndrome among 94,610 births was 0.87 per 1000, or 1 per 1150. Screening of 112,269 newborns for aminoacid disorders showed four disorders to be the commonest--tyrosinemia, maple syrup urine disease and phenylketonuria. Screening of cases of mental retardation for aminoacid disorders revealed four to be the commonest--hyperglycinemia, homocystinuria, alkaptonuria, and maple syrup urine disease. Metabolic studies of cases of mental retardation in AIIMS, Delhi and KEM Hospital, Mumbai, demonstrated that common disorders were those of mucopolysaccharides, lysosomes, Wilson disease, glycogen storage disease and galactosemia. It is estimated that beta- thalassemia has a frequency at birth of 1:2700, which means that about 9,000 cases of thalassemia major are born every year. Almost 5200 infants with sickle cell disease are born every year. Disorders, which deserve to be screened in the newborn period, are hypothyroidism and G-6-PD deficiency, while screening for aminoacid and other metabolic disorders could presently be restricted to symptomatic infants.