Most cases of Klinefelter’s syndrome remain undiagnosed and untreated. The key clinical feature of the condition is reduced testicular volume and this should be routinely measured as part of a male physical examination.
Klinefelter’s syndrome is a common genetic condition that affects one in 650 men worldwide; however, up to 70% of cases remain undiagnosed and therefore untreated for life. Klinefelter’s syndrome results from the presence of an extra X chromosome (47XXY) in the genome of the affected patient. Chromosomal mosaicism (the presence of both 47XXY and 46XY cells) occurs in about 10% of men who usually have milder or fewer features of Klinefelter’s syndrome, whereas the presence of additional X chromosomes (e.g. 48XXXY or 49XXXXY) is rare and associated with more severe signs and symptoms.