Klinefelter syndrome and other forms of primary testicular failure

Abstract

Klinefelter syndrome (KS) is the most common sex chromosome disorder in men affecting 1 in 400–600 males across all ethnic groups. Men with KS have at least one supernumerary X chromosome resulting in a 47, XXY genotype. KS can present in childhood, adolescence or adulthood with varying degrees of hypogonadism, gynecomastia, very small testes and azoospermia. In adults, FSH and LH levels are elevated, and testosterone levels are low or low normal. The diagnosis is confirmed by tissue karyotyping which usually reveals a 47, XXY genotype, although about 10% of men with KS phenotype are mosaic (47, XXY/46, XY), and infrequently additional X chromosomes are present. Treatment consists of testosterone replacement, and in the subset of patients in whom sperm are present on testicular biopsy, infertility can be treated by in vitro fertilization using intracytoplasmic sperm injection.