To determine whether the methylation status of these genes underwent alterations in early stage human PC, we compared β-values from publicly available database for all methylation loci (26, 5, 10 and 14 loci for KRAS, CDKN2A, TP53 and SMAD4, respectively) between early-stage PC and normal conditions. The gene discussed is CDKN2A; the disease is pachyonychia congenita.