Possible causes of fever and polyarthritis
Infectious arthritis: septic arthritis, bacterial endocarditis, Lyme disease, viral arthritis
Reactive arthritis: enteric infections, genitourinary infections
Systemic rheumatic diseases: RA∗, SLE∗, Still’s disease, systemic vasculitis
Crystal-induced arthritis: gout, pseudogout
Miscellaneous disease: malignancy, familial Mediterranean fever, rheumatic fever, dermatomyositis, sarcoidosis, Behcet’s disease, inflammatory bowel disease, Henoch–Schönlein purpura, Kawasaki’s disease, erythema nodosum, erythema multiforme, Whipple’s disease, relapsing polychondritis
∗Note that fever as a disease manifestation of RA and SLE is uncommon. In such patients, especially in the presence of immunosuppressive medications, a fever should be presumed secondary to infection until proven otherwise.