CDC73 and pachyonychia congenita: Germline HRPT2 mutations are also found in patients with familial isolated hyperparathyroidism and in up to 20 % of PC patients who have been primarily classified as sporadic [25], while somatic HRPT2 mutations are almost exclusively found in up to 77 % of sporadic PC and in less than 1 % of sporadic PA [4, 6, 7].