Pyrophosphate arthropathy: a clinical study of fifty cases.

Calcified deposits in joint structures have long been recognised radiographically and the early report of Werwath in 1928 drew attention to an association with synovitis. Further interest in the subject was stimulated by two clinical studies, the first presented in 1957 by Zitrian and Sit’aj (1963), who observed this combination in several families and named it “chondrocalcinosis articularis (familiaris)”. A second important contribution was made in 1962 by McCarty, Kohn and Faires as a result of studying the crystals present in the synovial fluid in cases regarded as gouty arthritis. In some joints, the radiographs of which frequently showed calcified deposits, the crystals were identified crystallographically as calcium pyrophosphate dihydrate (CPPD). The syndrome was consequently called “pseudo-gout”. During the following decade case reports of pyrophosphate deposition disease appeared from all over the world (McCarty, Hogan, Gatter and Grossman 1966; Currey, Key, Mason and Swettenham 1966; Webb, Champion, Frecker and Robinson 1970). The terminology has been heterogeneous, but the recently introduced terms “ pyrophosphate arthropathy” (Currey 1970, Russel et al. 1970) and “pyrophosphate synovitis” (Bjelle and Sund#{233}n 1971) seem appropriate. Although confirmation of the diagnosis of pyrophosphate synovitis is now a daily routine in many centres dealing with joint diseases, most reported series comprise few cases. In the larger series relatively few definite diagnoses have been made; in other words calcified deposits have been observed radiographically but the characteristic crystals not demonstrated by polarised light microscopy or by crystallography. In necropsy material McCarty et al. (1966) found that only half the deposits in menisci consisted of calcium pyrophosphate. It is therefore preferable to restrict the analysis of patients to those with a definite diagnosis. Since 1970 all patients with disorders of the knee joint of unknown cause or with calcification of joint structures who attended the Department of Orthopaedic Surgery of the University Hospital in Lund have been screened for the occurrence of pyrophosphate crystals in the synovial fluid by polarised light microscopy. A surprisingly high number of cases were detected (Bjelle and Sund#{233}n1971), and thus there seemed to be an urgent need for a systematic study of the clinical picture of pyrophosphate arthropathy. Fifty definite cases, recognised during a period of eighteen months, form the subject of this report.