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. Here, CTLA4 is linked to pachyonychia congenita.