The deficiency of 17 alpha-hydroxylase/17,20-lyase causes a rare autosomal recessive disorder presenting with congenital adrenal insufficiency (CAH) and sexual infantilism. Both 17 alpha-hydroxylase and 17,20-lyase reactions are catalyzed by a single polypeptide, cytochrome P450c17 (CYP17), which is encoded by the CYP17A1 gene. We describe the clinical, hormonal, and molecular findings of a 33-yr-old patient presenting with primary amenorrhea, late onset hypertension, and hypokalemic myopathy. The molecular analysis of CYP17A1 revealed a novel homozygous missense mutation resulting in the substitution of arginine to lysine at the amino acid position 21 (p.R21L).