Pseudogout masking other arthritides.

Of 314 patients with proved pseudogout, 9 had a separate serious disease in the same joint: 5 had septic arthritis, 2 rheumatoid arthritis, 1 psoriatic arthritis, and 1 hypertrophic pulmonary osteoarthropathy. In every instance but one, the episode of crystal synovitis appeared to be provoked by the new inflammatory process, disturbing previously asymptomatic chondrocalcinosis. Pseudogout attacks, although generally idiopathic solo events, can mask septic and chronic inflammatory arthritis.