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An XX male patient was examined for the presence of 25 loci on the Y chromosome. Only 2 loci, the proximal border of the pseudoautosomal region Y and the sex determining region Y, were detected in this patient. The other 23 loci, including the zinc finger protein Y, were absent. We presume that a crossing over between the X and Y chromosomes occurred at the region proximal to the sex determining region Y but distal to the zinc finger protein Y during meiosis of the father.

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 Yqll. 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.

Two XX male patients were examined for the presence of 25 Y-specific loci using Southern blot analysis and polymerase chain reaction techniques. They were phenotypically normal male patients, although 1 had bilateral undescended testes and 1 had hypoplastic testes. The former patient had 10 of 11 loci on the short arm, while the latter lacked any of the 25 Y-specific loci. These findings may suggest the existence of a nonY gene that is controlled by the testis-determining factor on the short arm of the Y chromosome and has a role in the testis formation in man.

A hypospadiac boy with a hypoplastic penis and an apparent 46,XX karyotype in blood and testis cultures is described. Exploratory laparotomy and bilateral gonadal biopsy revealed the presence of 2 testes in the right and 1 in the left hemiscrotum, each of which only showed hypoplastic testicular tissues histologically. Uncultured testis smears showed Y chromatin in approximately 20% of the cells. Also, the Southern blot and polymerase chain reaction analyses detected a weak but distinct signal of Y chromosome-derived deoxyribonucleic acid sequences in the perineal skin but not in the blood lymphocytes. The results indicated that the boy had a small proportion of Y chromosome-containing cells in the form of mosaicism in limited tissues, such as the testes and perineal skin. This finding may have implications in the genesis of testes in some cases of XX patients, and true hermaphrodites or male pseudohermaphrodites with an apparent 46,XX karyotype. To our knowledge, this appears to be the first case of polyorchidism with an identified chromosome abnormality.