This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
49,XXXXY syndrome is a type of chromosome abnormality characterized by the presence of 3 extra X chromosomes in males. It is sometimes referred to as a variant of Klinefelter syndrome, but differs from Klinefelter syndrome in many ways and is more severe. Signs and symptoms of 49,XXXXY syndrome can vary but may include learning difficulties or intellectual disability; low muscle tone; hypogonadism; infertility; delayed growth; distinctive facial features; and a variety of birth defects that may affect the heart, bones, brain and/or kidneys. It is usually not inherited and caused by a random error in cell division. Treatment depends on the features in each person and is often managed by a multidisciplinary team.
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