Finally, to pave the way for non/minimally-invasive diagnostic tests, future studies are also needed to investigate if hypermethylation of AOX1, CCDC181, GABRE, GAS6, HAPLN3, KLF8, MOB3B, and/or SLC18A2 can be detected also in urine and/or blood (plasma/serum) samples from PC patients, as has been reported for GSTP153. The gene discussed is GABRE; the disease is pachyonychia congenita.