CDKN2A and pachyonychia congenita: Not unexpectedly, most of the deleterious genes responsible for various well-defined cancer syndromes such as CDKN2A for the FAMMM syndrome, mismatch repair (MMR) for Lynch syndrome, TP53 for Li-Fraumeni syndrome, APC for familial adenomatous polyposis, and BRCA2 for the hereditary breast-ovarian cancer syndrome, indicate that the PC is part of each disorder’s cancer spectrum.