Klinefelter syndrome

Also known as: 47,XXY

Male hypogonadism due to an extra X chromosome.

Medical specialty: Endocrinology
Subspecialty: Endocrinology / Reproductive endocrinology
Sex & age distribution: Male: affected only; Female: not applicable; Children: yes, often diagnosed in adolescence or adulthood
Gene(s) involved: SHOX

Etiology & mechanism

Supernumerary X chromosome causes testicular failure.

Gene(s) involved (1)

SHOX

Symptoms & signs (9)

azoospermiadelayed pubertygynecomastiainfertilitylearning difficultieslow testosteronesmall firm testessparse body hairtall stature

SyndromeScope — educational reference. Content is model-generated and not clinically verified; always confirm against OMIM, Orphanet and GeneReviews before clinical use.