ESR1 and pachyonychia congenita: Under the subgroup analysis of ethnicity, we observed that ESRα rs9340799 was significantly associated with the susceptibility to PC in European population (AvsG, p = 0.000; AAvsGG, p = 0.002), while there was no difference in Asian (AvsG, p = 0.493; AAvsGG, p = 0.736) or African population (AvsG, p = 0.800; AAvsGG, p = 0.788).