Klinefelter-like phenotype and primary infertility in a male with a paracentric Xq inversion.

Klinefelter syndrome is an abnormality of sexual development which is usually characterised by the chromosome complement 47,XXY. We present a case of a male patient with the phenotypic appearance of Klinefelter syndrome and primary infertility, who was found, on karyotype analysis, to have a hitherto undescribed inversion of the long arm of the X chromosome (46,Y,inv(X)(q12q25)). The underlying genetic mechanisms responsible for his phenotype are unknown, but may include direct interruption of X chromosome genes around the breakpoint(s), a position effect, and/or impairment of normal chromosome pairing at meiosis.