| Essential (idiopathic) |
| Systemic rheumatic and autoimmune diseases |
| ANCA-associated vasculitis |
| Ankylosing spondylitis |
| Behçet syndrome |
| Familial Mediterranean fever |
| Giant cell arteritis |
| Graves' disease |
| Hashimoto's thyroiditis |
| Henoch-Schönlein purpura (immunoglobulin A vasculitis) |
| IgA nephropathy |
| Inflammatory bowel disease |
| Inflammatory muscle disease |
| Mixed connective tissue disease |
| Osteitis |
| Polyarteritis nodosa |
| Primary biliary cirrhosis |
| Psoriasis |
| Pyoderma gangrenosum |
| Rheumatoid arthritis |
| Sarcoidosis |
| Sjögren's syndrome |
| Systemic lupus erythematosus |
| Systemic sclerosis |
| Thromboangiitis obliterans (Buerger's disease) |
| Infectious diseases |
| Chlamydia |
| Colitis, infectious |
| Cytomegalovirus |
| Giardia |
| Hepatitis C |
| Herpes virus |
| HIV |
| Post-respiratory infection |
| Staphylococcus aureus |
| Streptococcus |
| Trypanosomiasis |
| Tuberculosis |
| Varicella-Zoster virus |
| SARS-CoV-2 infection/COVID-19 |
