Other Crystalline Arthritis

Besides monosodium urate and calcium pyrophosphate crystals, other crystals can deposit in the joints and cause arthritis. These include basic calcium phosphate (BCP) and calcium oxalate crystals.

• Apatite/BCP crystals may cause periarthritis, tendonitis, or a destructive arthritis. Shoulders are the most affected joint, either in the form of calcific periarthritis or with true joint arthritis, which is called Milwaukee shoulder.

• Hydroxyapatite complexes and BCP complexes can be identified only by electron microscopy and mass spectroscopy. Therefore, apatite disease should be suspected when no crystals are present in the

synovial fluid.

• Treatment of apatite disease is similar to that for pseudogout.