Dear Editor,rnY chromosome microdeletions (YCMs) occur when gene fragments are deleted from the azoospermia factor (AZF) gene that is located on chromosomal band Yq11.YCMs are the second most common genetic cause of male infertility following Klinefelter syndrome.1 Genetic screening of AZF is widely used in the diagnosis of male infertility.YCMs are primarily identified by screening six sites as indicated in the European Academy of Andrology and the European Molecular Genetics Quality Network (EAA/EMQN) guidelines,including AZFa (sY84 and sY86),AZFb (sY127 and sY134),and AZFc (sY254 and sY255).1 The AZFa region is mainly involved in spermatocyte proliferation and is considered as the most important region of AZF.2 Gene deletions in AZFa are rare,account for 0.5％-4.0％ of all YCMs,and include complete as well as partial deletions.1 Patients with a complete AZFa deletions are azoospermic,and thus standard biopsy examination is futile.1 The proximal end of the AZFb region contains numerous palindromic sequences,and deletions in this region often cause the loss of large gene fragments.