For example, in sarcoidosis, a related disease of IgG4-RD, PLA2R-positive MN is frequently observed in active sarcoidosis, which suggests the existence of a causal relationship in which the immunological status of sarcoidosis may induce immunization against PLA2R [20]. The gene discussed is PLA2R1; the disease is immunoglobulin G4-related sclerosing disease.