Several genetic mutations have been proposed in PC, including, retinoblastoma (RB), P53, cyclin D1/parathyroid adenomatosis gene 1 (PRAD1), and BRCA2; however, a strong body of evidence implicates the gene CDC73 (formerly called HRPT2) first identified in the context of HPT-JT [7,8,9]. The gene discussed is CCND1; the disease is pachyonychia congenita.