Screening of congenital hypothyroidism, phenylketonuria, galactosemia, homocystinuria, and maple syrup urine disease in moderate to severe mentally retarded Chinese children.

Five-hundred and fifty one mentally retarded children from seven institutes in Northern Taiwan were screened by dried blood spot for the detection of treatable congenital metabolic diseases, including congenital hypothyroidism, phenylketonuria, homocystinuria, maple syrup urine disease and galactosemia. We found 2 children (0.36%) with congenital hypothyroidism, 1 case (0.18%) of classical phenylketonuria and two cases (0.36%) of trisomy 21 associated with autoimmune thyroiditis. The results of our investigation suggest that congenital hypothyroidism and phenylketonuria can be the factors causing mental retardation among children in Taiwan and mass neonatal screening of these treatable inborn metabolic diseases is strongly indicated for efficiently circumventing mental retardation in our community.