This section describes the three aberrantly methylated genomic loci, PITX2, C1orf114, and GABRE~miR-452~miR-224, as well as the three-gene marker panel AOX1/C1orf114/HAPLN3, for which there is currently the strongest experimental support for a prognostic biomarker potential in PC. Here, HAPLN3 is linked to pachyonychia congenita.