PDCD1 and pachyonychia congenita: The expression pattern of ICI (such as programmed cell death protein 1 (PD-1), programmed cell death protein ligand 1 (PDL-1), and citotoxyn T-lymphocyte-associated protein 4 (CTLA4)) in the PC microenvironment is not well understood, and several clinical trials are nowadays focusing on the characterization of the microbiome and its role in PC in the immunological field.