The syndromic and hereditary forms of PC are associated with germline mutations of the cell division cycle 73 (CDC73) gene, also referred to as the hyperparathyroidism type 2 (HRPT2) gene, MEN type 1 (MEN1), and rearranged during transfection (RET) genes (Table 1). Here, MEN1 is linked to pachyonychia congenita.