CHEK2 and pachyonychia congenita: In a sequencing study of 8 PC-associated genes (ATM, BRCA1, BRCA2, BRIP1, CHEK2, HOXB13, NBN and PALB2) in 7636 unselected Japanese PC patients and 12,366 non-cancer male controls, the overall mutation prevalence was 2.9% in patients versus 0.8% in controls (including BRCA, 1.1% vs. 0.2%, respectively) [18].