A 17-year-old boy is brought to the office for evaluation of bilateral breast enlargement. He first noticed it a few months ago and says that it is slightly painful. His parents are concerned that his breasts are gradually becoming more prominent. The patient is in special education classes due to a long-standing history of learning disabilities. His father has type 2 diabetes mellitus and is on dialysis for chronic renal failure. Height is at the 95th percentile, and weight is at the 25th percentile for age and sex. Symmetrical glandular tissue is palpated under both nipple-areolar complexes. His sense of smell is normal, and his testicles are small and firm. Laboratory evaluation would most likely show which of the following findings?

Question

A 17-year-old boy is brought to the office for evaluation of bilateral breast enlargement.  He first noticed it a few months ago and says that it is slightly painful.  His parents are concerned that his breasts are gradually becoming more prominent.  The patient is in special education classes due to a long-standing history of learning disabilities.  His father has type 2 diabetes mellitus and is on dialysis for chronic renal failure.  Height is at the 95th percentile, and weight is at the 25th percentile for age and sex.  Symmetrical glandular tissue is palpated under both nipple-areolar complexes.  His sense of smell is normal, and his testicles are small and firm.  Laboratory evaluation would most likely show which of the following findings?

Quizplus · Accepted Answer

11ec160b_39a0_bf89_9249_ef8b6572a697_MD0001_00 Klinefelter syndrome (KS) is caused by sex chromosome aneuploidy, which most commonly results in a 47,XXY karyotype. These patients typically have atrophied, hyalinized seminiferous tubules (resulting in low inhibin levels) and damaged Leydig cells (resulting in low testosterone levels). The lack of feedback inhibition results in excess gonadotropins (increased LH and FSH), which in turn increase estrogen levels (Choice A). Primary hypogonadism is the cardinal feature. Phenotypic findings include azoospermia, small/firm testes, absent secondary male characteristics (including deep voice, beard, and male-pattern pubic hair), and tall stature. Gynecomastia is also common and associated with a risk of malignant transformation. Cognitive impairment is characterized by learning and socialization difficulties. (Choice B) Increased androstenedione levels due to anabolic steroid abuse can cause irreversible gynecomastia and testicular atrophy. Exogenous steroid use can be distinguished from KS by the additional findings of acne, male-pattern baldness, hastened epiphyseal closure (reduced height potential), and aggressive behavior. (Choice C) Testicular germ cell tumors produce excessive β-hCG, resulting in gynecomastia in addition to a firm, rapidly growing testicular mass. (Choice D) Chronic renal insufficiency is marked by high creatinine and uremia. Uremia is toxic to the testicles and suppresses testosterone production. Renal abnormalities are not a typical feature of KS. (Choice F) Antipsychotics (eg, haloperidol) can cause hyperprolactinemia, which in turn can induce gynecomastia. Excess prolactin is also secreted from prolactinomas. Prolactin levels are not typically elevated in other causes of gynecomastia. (Choice G) Gynecomastia is commonly seen in cirrhosis, particularly in the setting of alcohol abuse. The estrogen-to-testosterone ratio is disrupted due to impaired hepatic degradation of estrogens in addition to ethanol's direct inhibition of testosterone production. Patients with cirrhosis are often coagulopathic due to diminished clotting factor production, which results in increased prothrombin time/International Normalized Ratio. Educational objective: Patients with Klinefelter syndrome (47,XXY) have primary hypogonadism characterized by low testosterone and elevated gonadotropin (FSH, LH) levels. In addition, elevated estradiol results in the common finding of gynecomastia. __________ References: Klinefelter syndrome: the commonest form of hypogonadism, but often overlooked or untreated. (http://www.ncbi.nlm.nih.gov/pubmed/23825486) Phenotypic differences in mosaic Klinefelter patients as compared with non-mosaic Klinefelter patients. (http://www.ncbi.nlm.nih.gov/pubmed/24502895) Clinical review: Klinefelter syndrome--a clinical update. (http://www.ncbi.nlm.nih.gov/pubmed/23118429)

A 17-Year-Old Boy Is Brought to the Office for Evaluation