Newborn screening for 21-hydroxylase deficiency: results of CYP21 molecular genetic analysis. 
Blood samples for plasma steroid hormone determinations and molecular genotype analysis of the 21-hydroxylase gene (CYP21) were obtained from 15 infants identified through a voluntary newborn screening program.  Mutations were identified on both CYP21 alleles in 12 (80%) of 15 infants; all had confirmatory plasma 17-hydroxyprogesterone concentrations > 3500 ng/dl.  No patient was found to carry mutations associated with late-onset 21-hydroxylase deficiency.  Newborn screening hastened diagnosis in eight infants.