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A 17-year-old male is evaluated for tall stature, gynecomastia, and small testes. He has mild learning difficulties, particularly with language. Hormone testing reveals elevated FSH/LH with low testosterone.
- Karyotype: 47,XXY (most common)
- Variants: 48,XXXY; 48,XXYY; 49,XXXXY; mosaic 46,XY/47,XXY
- Tall stature with long limbs
- Small, firm testes; infertility (azoospermia)
- Gynecomastia
- Learning disabilities (often language-based)
- Increased risk: breast cancer, extragonadal germ cell tumors, metabolic syndrome
- Karyotype
- Often diagnosed in adulthood during infertility workup
- Testosterone replacement starting at puberty
- Educational support
- Fertility options: testicular sperm extraction + IVF may be possible
Klin-FE-lter = FEminization: Gynecomastia is a hallmark feature (20x increased risk of male breast cancer). Primary hypogonadism: small testes, elevated LH/FSH, low testosterone. No increased risk for testicular cancer, but 50x increased risk for mediastinal germ cell tumors.