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NORD is very grateful to Jeannie Visootsak, MD, FAAP, Associate Professor, Developmental-Behavioral Pediatrics, Department of Human Genetics & Pediatrics, Emory University School of Medicine, for assistance in the preparation of this report.
Synonyms of Klinefelter Syndrome
- XX male
- XXXXY male
- XXXY male
- XXY male
- XXYY male
- No subdivisions found.
Klinefelter syndrome is a group of chromosomal disorders in males in which one or more extra X chromosomes are present. Males with the classic form of the disorder have one extra X chromosome. Males with other X and Y variations have additional X and/or Y chromosomes. The extra X and/or Y chromosome can affect physical, developmental, behavioral, and cognitive functioning. Common physical features may include tall stature, lack of secondary pubertal development, small testes (hypogonadism), delayed pubertal development, and breast development (gynecomastia) in late puberty. These features may be associated with low testosterone level and elevated gonadotropin levels.
Klinefelter Syndrome Resources
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