Arthritis associated with adult onset Stills disease
The arthritis associated with adult onset Stills disease may be overshadowed by the systemic features of the illness. It may not be present at the time of disease onset, may involve only a few joints, or be fleeting. With time, the arthritis frequently becomes polyarticular affecting both small and large joints.
The joints involved in descending order include: knees, wrists (very common), ankles, elbows, proximal interphalangeal, shoulders, metacarpophalangeal, metatarsophalangeals, hips, distal interphalangeal, sacroiliac, and temporomandibular joints.
Neck pain is seen in 50% cases. Arthrocentesis generally yields a class II inflammatory synovial fluid (mean 13,000 cells/μL), and radiographs usually reveal soft-tissue swelling, effusions, and occasionally periarticular osteoporosis. Joint erosions and/or fusion of the carpal bones (40%–50%), tarsal bones (20%), and cervical spine (10%) may be seen but are more common in children than adults. A destructive arthritis occurs in up to 20% to 25% of cases. Patients with the chronic articular presentation of AOSD will frequently have less intense fevers and typically lower ferritin levels.
