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.).