Late onset 21-hydroxylase deficiency in a girl mimicking true sexual precocity

Complete sexual precocity as a presenting symptom of untreated classical congenital adrenal hyperplasia (CAH) is rare and has never been reported in the late onset type. A six-year-old girl presented with early breast and pubic hair development and 17 β-estradiol (E2) levels of 75 pg/ml. The diagnosis of late onset 21-hydroxylase deficiency was confirmed by the levels of (17-OHP) (basal level 425 ng/dl; following ACTH stimulation — 3250 ng/dl) and the HLA type of b14 DR1. Following treatment with 20–25 mg/m2 of hydrocortisone acetate the plasma E2 level rapidly fell to < 10 pg/ml. It is suggested that the premature breast development was induced by increased adrenal estrogen production or increased peripheral aromatization of the high levels of adrenal androgens.