[Klinefelter's syndrome associated with precocious puberty due to tumoral secretion of chorionic gonadotropins].

A 8 and a half year-old boy presented with precocious puberty related to a malignant thoracic teratoma. He was also shown to have a Klinefelter syndrome. Precocious puberty related mainly to the liver, intracranial or thoracic tumors is rare. It seems to be exclusively observed in boys. The slight testicular enlargement is the main clinical sign. The contrast between high LH and low FSH levels is the most striking biological data. The diagnosis is proved by plasma HCG, beta-HCG and alpha-foetoprotein determination. Our patient is the third one with Klinefelter syndrome; this this association is certainly not fortuitous.