Review Question - QID 106498

This patient's clinical findings are most consistent with Klinefelter syndrome. This is a genetic disorder in which patients have an extra X-chromosome and a karyotype of 47, XXY.

Klinefelter syndrome is caused by the presence of an additional X-chromosome. Affected individuals are typically asymptomatic throughout childhood and present in adolescence or early adulthood. The typical clinical presentation includes tall stature, small testes, and gynecomastia. Further workup reveals a 47, XXY karyotype and typically, azospermia. Almost all men with Klinefelter syndrome are infertile. Late onset of puberty should prompt further evaluation, however often at diagnosis, the window for any therapeutic interventions has passed.

Wattendorf and Muenke discuss the epidemiology of Klinefelter syndrome in their review. Approximately 1 in 1,000 boys will have Klinefelter syndrome. Ten percent of cases are diagnosed before birth and 25% are identified during adulthood. Klinefelter syndrome is also common among infertile men, with an incidence of 5 to 10%.

Gies et al. discuss medical management of those with Klinefelter syndrome. There is often involution of the testes during puberty. To ensure proper sexual development and prevent against deleterious effects of hypogonadism, preventative testosterone supplementation can be provided to adolescents. While this treatment has been supported in the literature, there have yet to be any randomized clinical trials examining the treatment.

Figure A demonstrates classic findings of Klinefelter syndrome including tall stature, gynecomastia, and small testes.

Incorrect Answers:
Answer 1: Unless another chromosome other than a sex chromosome is missing, this is not an actual karyotype.
Answer 3: This is the cause of over 95% of cases of congenital adrenal hyperplasia, of which manifestations may range from severe salt wasting and virilization of female genitalia prenatally to excess androgen effects and infertility depending on the severity of enzyme deficiency.
Answer 4: In cases of androgen insensitivity, affected individuals are genetically male, but have female genitalia and habitus.
Answer 5: This is the karyotype of Turner's Syndrome.