Crystal deposition disease.

Calcium pyrophosphate dihydrate crystal deposition disease and HA crystal deposition disease are two common disorders that may come to the attention of a physician because of a variety of clinical symptomatology patterns. In CPPD crystal deposition disease, characteristic radiologic features include articular and periarticular calcification and an arthropathy consisting of joint space narrowing, bone sclerosis, often prominent subchondral cyst formation, occasional severe and progressive destructive bone changes, and variable osteophyte formation. These findings are often seen in a characteristic distribution with involvement of non-weight-bearing as well as weight-bearing joints and with involvement of distinctive intraarticular sites such as the patellofemoral compartment of the knee and the radiocarpal compartment of the wrist. In HA crystal deposition disease, characteristic radiologic features consist of calcific tendinitis and periarthritis as well as a more recently described arthropathy. Awareness of the distinctive roentgenographic appearance of these two diseases should allow a specific diagnosis to be made, and an understanding of their pathologic features should aid in appropriate therapy and guide future investigation of possible etiologic factors.