Chondrocalcinosis

Abstract

Abstract This review covers a number of linked pathological, radiological, and clinical entities, and it is this linkage of conceptually distinct entities that creates confusion in determining epidemiology (Fig. 13.1). There are also differences in the use of nomenclature and, at the time of writing, there is a lack of international agreement. The pathological entity is deposition of calcium salt crystals in articular, including meniscal, cartilage. The crystals are predominantly of the calcium phosphate family (McCarty et al. 1%2), mainly calcium pyrophosphate dihydrate (CPPD), though other calcium salts are found including hydroxyapatite (McCarty et al. 1966). CPPD crystal deposition can be one cause of the radiological observation of chondrocalcinosis, that is the radiological appearance of calcified deposits in specific cartilaginous sites such as the meniscal cartilages of the knee, wrist, pelvis, and other peripheral joints. Clinically most of the calcified deposits are silent but the syndrome of pseudogout* is well recognised of an acute mono or oligoarthritis, resembling gout but where the synovial fluid contains CPPD crystals rather than urate ones. The diagnosis of pseudogout is normally based indirectly on finding crystals in the synovial fluid which, under polarized light, are either weakly or negatively birefringent compared to the positive birefringence of urate crystals. In addition to the clinical presentation of pseudogout there are a number of other clinical patterns of presentation. These include (i) a polyarticular osteoarthritis, though the exact relationship between CPPD and osteoarthritis is unclear (Dieppe et al. 1982), (ii) a widespread inflammatory polyarthritis mimicking rheumatoid arthritis (including, in IO per cent, a positive reaction for rheumatoid factor), and (iii) rarely a neuropathic picture resembling a Charcot joint (McCarty 1975). Uric acid arthropathy probably co-exists with CPPD arthropathy greater than expected by chance (McCarty 1975). The terms pyrophosphate arthropathy (Europe) and CPPD crystal deposition disease (USA) are used interchangeably which hinders understanding.