Congenital adrenal hyperplasia with 47, XXY Klinefelter syndrome.

We describe here a unique case of congenital adrenal hyperplasia (CAH) accompanied by Klinefelter syndrome. A Japanese boy was diagnosed as having CAH caused by 21-hydroxylase deficiency at birth, but was untreated thereafter until age 10. In the meantime he showed marked acceleration in somatic growth with sexual precocity by age 9, at which time growth completely stopped. During regular follow-ups at our clinic and steroid treatment after age 10, he was recognized as having bilateral small and firm testes. A chromosomal examination and a testicular biopsy revealed a complication of 47, XXY Klinefelter syndrome with CAH. Association of these two diseases has not been reported so far, and the present case is the first one to our knowledge.