The estimated rate of loss of parafibromin IHC expression of PC was 0.522 (95% CI: 0.444–0.599) and was significantly higher than those of APA (0.291, 95% CI: 0.207–0.391), PA (0.027, 95% CI: 0.011–0.064), and parathyroid hyperplasia (0.032, 95% CI: 0.008–0.119) (Table 2). Here, ENPEP is linked to pachyonychia congenita.