A minute deletion of the Y chromosome in men with azoospermia.

We analyzed deoxyribonucleic acid from 50 Japanese men with azoospermia whose Y chromosomes were cytogenetically normal. A total of 26 loci was examined in each patient. Of these patients 6 had small interstitial deletions, each of which was located within the distal part of Yq11. Five of these 6 patients lacked the same 2 loci, DYS7C and DYS1, while 1 patient had a larger deletion including DYS7C but not DYS1. More than 10% of all men with azoospermia of unknown origin may have minute interstitial deletions of the Y chromosome surrounding the DYS7C locus. The proximal part of this zone presumably encompasses the gene deletion that causes azoospermia.