<unk>  occurs as often in men as in women. In a Mayo Clinic series, the annual incidence was about 3.5 cases per million. The highest incidence is between the ages of 40 and 50 years, but it may occur at any age.
Relapsing polychondritis
Rheumatoid nodulosis
Reactive arthritis
Juvenile idiopathic arthritis
Psoriatic arthritis
Discoid lupus erythematosus
Polymyalgia rheumatica
Rheumatoid arthritis