The proportion of germline BRCA1/2 mutation carriers among patients with any stage PC was available from 29 articles, for a total of 33,784 patients, and was equal to 4.47% (95% CI: 3.38–5.70), with significant heterogeneity (I2 = 95.57%; p < 0.0001) (Figure 4a). The gene discussed is BRCA1; the disease is pachyonychia congenita.