Most common congenital anomaly causing primary hypogonadism
Additional X chromosome in males, with most common karyotype 47,XXY (80–90%)
Causes cognitive, social, behavioral, and learn...
Prenatal testing (10%)
Newborn: hypotonia, genital abnormalities
Adolescence: delayed or absent puberty, persistent gynecomastia, small testes, learning disabilities, psychosocial probl...
Preventive dental care
Calcium and vitamin D supplementation
Develops secondary male sex characteristics
Metabolic screening every 3 months and then annually: lipids, glucose, and thyroid function
Annual clinical breast exam ± breast imaging
Davis S, Howell S, Wilson R, et al. Advances in the interdisciplinary care of children with Klinefelter syndrome. Adv Pediatr. 2016;63(1):15–46. [View Abstract on OvidMedline]
Q98.4 Klinefelter syndrome, unspecified
Q98.1 Klinefelter syndrome, male with more than two X chromosomes
Q98.0 Klinefelter syndrome karyotype 47, XXY
Q98.5 Karyotype 47, XYY
Q98.3 Other male w...
KS males have ≥1 additional X chromosome (XXY karyotype) with associated features of hypergonadotropic hypogonadism.
Accounts for 3% of male infertility
Most men do not have “textbook fe...
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<bold><italic>Figure 7-16</bold> Clinical features of Klinefelter syndrome (47,XXY).</bold>