45,X/46,XY/47,XY, +21 mosaicism in a hypogonadal phenotypic male.

A phenotypically normal male was found to have a chromosomal complement of 45,X/46,XY/47,XY, +21. This mosaic pattern has been reported only twice before. Although the patient had apparently fathered two children, he now has progressive impotence, absence of sperm in the seminal fluid, atrophic testes, almost complete absence of germ cells in testicular biopsies, high plasma LH and FSH, and a low normal testosterone. There were no physical characteristics of Turner's or Down's syndromes except for dermatoglyphic features commonly associated with the latter. These observations in this patients emphasise the value of chromosomal studies in multiple tissues in cases of mosaicism with atypical clinical features.