FKBPL and Infertility: The frequency of alterations in FKBPL in the azoospermic populations is not inconsistent with the frequencies seen for other human genes implicated in infertility, such as Y chromosome microdeletions (2-20% of infertile males [3]) or in particular the other autosomal genes such as SYCP3 (heterozygous mutations in 2/19 infertile males [36]); USP9 (17/576 patients or 3% [37]) and Protamine 1 (heterozygous mutations in 1-10% of patients [38,39].