Klinefelter syndrome (KS), characterized by the presence of at least one extra X chromosome, is the most common chromosomal abnormality in males. Nevertheless, it is highly underdiagnosed (only 25% of expected diagnoses) or is diagnosed later in life, usually around 30 years. KS is associated with increased morbidity resulting in loss of life of about 2 years with an increase in mortality due to many different diseases. The main findings of KS are: small testes, hypergonadotropic hypogonadism, and cognitive impairment. Hypogonadism may lead to changes in body composition and the risk of developing
metabolic syndrome and type 2 diabetes. KS is often accompanied by a language processing deficit for which the boys with KS often need speech therapy or even school support, while not showing in general a real cognitive disorder. Medical treatment consists in testosterone replacement therapy to counteract the systemic effects of hypogonadism and to treat or even prevent the frequent comorbidity
