Ann Rheum Dis 78 (3): 406 - 412, 2019. doi: 10.1136 / annrheumdis-2018 - 214603 Etiology of IgG4-Related Disease The cause of IgG4-RD is unknown, but is thought to involve autoimmunity because of its chronic, insidious nature, the targeting of self-proteins by antibodies (1), and responsiveness to immunosuppression.