Morbidity and mortality in Klinefelter syndrome (47,XXY)

Abstract Klinefelter syndrome (KS) (47,XXY) is the most common sex chromosome disorder in man and is a relatively common cause of male infertility and hypogonadism. The syndrome has been known since 1942, and many reports of different diseases associated with KS have been reported since that, but a more systematic knowledge about the long‐term outcome was not described until the last decade, where nation‐wide epidemiological studies were reported from Britain and Denmark. We here review the epidemiological data from two cohorts of patients with KS in Denmark and Britain, showing a significant increase in both mortality and morbidity from a variety of different causes. Mortality was increased by 50% (SMR 1.5 or HR 1.4) corresponding to a median loss of approximately 2 years. The risk of being admitted to hospital with any diagnosis was increased by 70%. The underlying reason for the poorer health in KS may be caused by interaction of genetic, hormonal and socio‐economic factors. Conclusion: Both morbidity and mortality are significantly increased in Klinefelter syndrome with a 50% increase in mortality risk and a 70% increase in risk of being admitted to hospital.