Classically, very high calcium levels above 14–15 mg/dL accompanied by PTH levels more than five times above the upper normal limit, high ALP > 285 IU/L, significantly decreased 1/3 radius BMD or gland diameter > 3 cm should raise the suspicion of PC in PHPT patients [1,15,46,63]. This evidence concerns the gene PTH and pachyonychia congenita.