CLDN1 and Obstructive azoospermia: Pathogenic non- and missense mutations have been described for many claudins including CLDN1 (NISCH syndrome), −2 (obstructive azoospermia), −5 (alternating hemiplegia), −10 (HELIX syndrome), −14 (DFNB29 deafness), −16 and −19 (both FHHNC syndrome) [1,27,86].