Klinefelter Syndrome

**Definition:** A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and male infertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tall stature. GYNECOMASTIA is present in many of the patients. The classic form has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns ( 46,XY/47,XXY; 47,XXY/48,XXXY, etc.).

**Tree numbers:** - C12.050.351.875.253.795.500 - C12.200.706.316.795.500 - C12.800.316.795.500 - C16.131.260.830.835.500 - C16.131.939.316.795.500 - C16.320.180.830.835.500 - C19.391.119.795.500 - C19.391.482.629

**Synonyms:** - Klinefelter's Syndrome - XXY Syndrome