Aortic involvement: Giant cell arteritis Retroperitoneal involvement: Lymphoma, sarcoma, granulomatosis with polyangiitis, Erdheim-Chester disease Lymphadenopathy: Sarcoidosis, lymphoma, Rosai-Dorfman disease, Erdheim-Chester disease Classification criteria for IgG4-RD published in 2019 (1), include 32 exclusion criteria that can help in making a differential diagnosis.