Polyarthritis
1) Gonococcal - Therapeutic trial of pencillin may help in diagnosis of gonococcal infection.
2) Viral infections such as rubella and hepatitis B may have polyarthritis.
3) Septic arthritis - Blood cultures may grow organisms.
4) Tuberculosis - It is usually mono-articular.
5) Juvenile rheumatoid arthritis - Here there is small joint involvement which lasts for 6 to 12 weeks and valvular involvement is rare. However, pericarditis alone may be seen.
Eventually deformities occur. Rheumatoid factor may be positive.
6) Serum sickness due to drug allergy, e.g., after penicillin injection may present as polyarthritis.
7) Infective endocarditis may mimic ARF as arthritis and carditis are common features. Joint involvement is usually mono-articular affecting large joints. Blood cultures if positive confirm the diagnosis.
8) Henoch Schonlein purpura, inflammatory bowel disease (ulcerative colitis, crohn's diseases), blood disorders (sickle cell anaemia, haemophilia, leukaemias), seronegative arthritis, Takayasu's arteritis may mimick ARF.