Reactive arthritis induced by parasitic infestation.

Arthritis developed in two patients during the course of parasite infestation with Strongyloides stercoralis and Taenia saginata, respectively. The joint involvement was polyarticular and symmetrical but seronegative and nonerosive radiologically. We found evidence of abnormal humoral immunity to the parasites, immune complexes in serum and synovial fluid, and immunoglobulin deposits in the synovia. Nonsteroidal anti-inflammatory agents proved ineffective but specific antiparasitic treatment resulted in resolution of the symptoms and immunologic abnormalities. Our findings provide further documentation of the interaction between the body's immune system and parasites and suggest that arthritis induced by parasitic infestation may be mediated by immune complex formation in susceptible hosts.