[Klinefelter syndrome affects mostly boys. An underdiagnosed chromosome abnormality].

Although Klinefelter's syndrome is the most common sex chromosome anomaly, affecting one in 5-800 boys, our knowledge of the syndrome is still poor. This is reflected in the paucity of published literature as compared, for example, with the vastly greater number of publications on Turner's syndrome with its lower incidence of 1/2,500 girls. Klinefelter's syndrome is manifestly underdiagnosed. Existing knowledge mainly derives from cases characterised by prominent symptomatology. Early diagnosis is important if additional support and resources are to be made available to the patient and his family. Testosterone replacement therapy should be initiated as soon as clinical and laboratory evidence becomes available. In selected cases, testosterone treatment can be started already during adolescence. At present, there is no established treatment for the infertility which almost always accompanies the condition.