CHEK2 and pachyonychia congenita: Of these, 103 patients (8.6% of the total sample) carried germline pathogenic variants in genes that have been definitively linked to an increased risk of PC or other types of cancers (BRCA2, ATM, CHEK2, NBN, BRCA1, PALB2, BRIP1 and BARD1) [32,33,34].