In a retrospective study of 131 Japanese patients with pHPT (111 with benign parathyroid lesions and 20 with PC), those with PC exhibited significantly higher mean serum calcium (12.7 mg/dL vs. 11.6 mg/dL) and PTH levels (397 pg/mL vs. 228 pg/mL) compared with benign cases [12]. This evidence concerns the gene PTH and pachyonychia congenita.