Ease Into Prep with a PANCE^® Question of the Day

The correct answer is D. This patient has Klinefelter syndrome. It is best diagnosed with a 47,XXY karyotype, though variants with 46,XY exist. The condition is characterized by small testes, disproportionately long arms and legs (secondary to delayed epiphyseal plate closure in puberty), infertility, and gynecomastia. Mental retardation and learning disability are common. Many men are not diagnosed until adulthood when they seek medical attention for infertility. Our patient clearly has these traits.

Patients who have Klinefelter syndrome often have an unexplained increase in follicle-stimulating hormone and luteinizing hormone. This increase occurs even in patients who have normal testosterone levels. Low follicle-stimulating hormone, luteinizing hormone, and testosterone (choice A) are typical for a secondary form of hypogonadism. Secondary hypogonadism is not associated with gynecomastia, because patients don't have an increase in conversion of testosterone to estradiol, which is stimulated by follicle-stimulating hormone and luteinizing hormone.

A prolactinoma (choice B) can certainly explain infertility, although it does not explain the patient's other physical findings.

An increased ratio of luteinizing- to follicle-stimulating hormone (choice C) describes polycystic ovary disorder and is not present in men.

Finally, 21-hydroxylase deficiency (choice E) causes an increase in androgen production, which our patient does not have. This condition is associated with late-onset female virilization.

PEARL: Klinefelter syndrome is characterized by 2+ X chromosomes and one Y chromosome, typically an XXY karotype. GnRH, LH, and FSH are elevated. Men develop gynecomastia from increased FSH and LH, and 25% have impaired mental development . Treatment is typically testosterone for helping to support the male endocrine system.