Bacterial infections: the arthritis of leprosy.

Arthritis is a common feature of leprosy and contributes to disability. Direct invasion of joints and bones by mycobacteria may lead to a destructive arthritis in lepromatous disease. The infective process may involve few or many joints. Reactional states may occur spontaneously but usually after the initiation of anti-mycobacterial treatment. In both the type 1 reaction of borderline case and the type 2 reaction of the lepromatous disease, intense inflammation may occur at sites of infection. The immunology of the reactions is different but they share clinical features including a polyarthritis which may resemble rheumatoid disease. The joint disease may be chronic or relapsing, affecting the wrists and small joints of the hands in particular. Radiological erosions may occur. Mycobacterium leprae is not found in the synovium in this pattern of arthritis. Further study of this phenomenon might yield useful information above the mechanism of joint inflammation in other rheumatic diseases.