Definition (Am Fam Physician 2005;72:2259)
• Usually 47, XXY karyotype. Can include extra X chromosomes or Y chromosomes
• Nondisjunction during meiosis with origin from either parent
• 1:1,000 boys; mosaicism in 15% of men
Diagnosis (Int J Endocrinol 2012; PMID 22291701)
• Males present w/ infertility or gynecomastia as teens or adults
• 50% <18 yo w/ mild neurodevelopmental disorders
• Late or incomplete puberty should prompt a workup
• FSH and LH nml in pre-pubertal pts, then high from mid-puberty w/ low testosterone
• Karyotype to count sex chromosomes in 50 cells (in case of mosaicism)
Clinical Manifestations
• Almost all men are infertile (3% of all male infertility)
• Testosterone def, small testes, ↓ facial hair, gynecomastia, ↓ pubic hair, and small penis
• Tall and slender with long legs and short torso
• May develop osteoporosis
Management
• Neurodevelopmental evaluation at diagnosis
• Hormone therapy for low testosterone levels or if hypergonadotropism is present
• Gynecomastia predisposes men to breast cancer; frequency 20–50×s > in normal men