However, recently Oud and colleagues showed in a larger study cohort of 2740 patients with azoospermia or severe oligozoospermia, that HIWI D-box variations are less frequent than proposed by Gou and colleagues, and the that loss of function of PIWI-LIKE 1 is unlikely to cause fertility impairments when haploin-sufficient [28]. Here, PIWIL1 is linked to Azoospermia.