Ring chromosome 21 and monosomy 21 mosaicism in a patient with azoospermia

In this report, we describe a patient with azoospermia in conjection with de novo ring chromosome 21 and monosomy 21 mosaicism. Inter-phase fluorescence in situ hybridisation (FISH) studies on uncultured peripheral blood and epithelial cells obtained by buccal smear revealed that 25% of the uncultured blood cells and 11% of the epithelial cells were monosomic for chromosome 21. Y chromosome microdeletion analysis ruled out the presence of any genomic deletions in the azoospermic factor a,b,c regions on the long arm of chromosome Y. Additionally, through subtelomeric FISH analysis, it was found that there was no deletion in the subtelomeric region of ring chromosome 21. Our results indicate that ring chromosome 21 is a rare, but recurrent chromosomal abnormality in male factor infertility. Furthermore, in individuals with ring chromosome 21, defective spermatogenesis is not associated with the deletion of any gene or genes located in the subtelomeric region of chromosome 21.