refers to the presence of an additional X chromosome in a person's body cells. Some individuals with a 47, XXY chromosome finding do not appear different from other individuals, and they may have mild symptoms or no apparent symptoms. During the first few years of life, most 47, XXY males do not show any obvious differences from typical male infants and young boys. Children may have slightly weaker muscles, delayed development of motor skills, and learning and/or language problems. In later adolescence and adulthood, 47, XXY males can have features of Klinefelter syndrome, which can include primary hypogonadism (decreased testosterone production), small testes, enlarged breast tissue (gynecomastia), tall stature, and/or other features. Although the vast majority of individuals with 47, XXY identify as males, some develop atypical gender identities. There have been reports of individuals with 47, XXY having a female physical appearance, but in most cases this was attributed to changes in specific genes related to sexual development. Most 47, XXY males are infertile, but many produce sperm and may be able to conceive with assisted reproduction. Treatment varies among individuals and may include testosterone therapy; however, this therapy may not be appropriate for all individuals.
Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.Description Last Updated: Dec 26, 2013