SRD5A1 and pachyonychia congenita: Although previous studies have showed the increased importance of SRD5A1 compared to SRD5A2 in advanced PC [22] as well as increased expression of SRD5A1 in metastatic PC compared to primary tumors [3,21,23,24], this study is the first to suggest further increased expression of SRD5A1 specifically in CRPC.