MLH1 and pachyonychia congenita: The increasing risk for PC has been shown to be associated with inherited germline mutations for particular genes, such as Breast cancer 1/2 (BRCA1/2), ataxia–teleangiectasia mutated serine/threonine kinase (ATM), serine/threonine kinase 11 (STK11), serine 1/2 (PRSS1/PRSS2), serine protease inhibitor Kazal-type 1 (SPINK1), the partner and localizer of BRCA2 (PALB2) and DNA mismatch repair genes, such as MutL homolog 1 (MLH1), MutS protein homolog2 (MSH2), MutS homolog 6 (MSH6) and the mismatch repair endonuclease PMS2 [10,11,12,13].