Hydroxyapatite deposition disease (Q44293)

Calcium hydroxyapatite crystal deposition disease is characterised by the presence of basic calcium phosphate crystals - predominantly hydroxyapatite - in periarticular soft tissues, especially tendons. This entity is best recognised as "calcific tendinitis" at its most frequent site about the shoulder, but the disease involves numerous other sites and may be more appropriately termed calcific periarthritis.