Crystal arthropathies

Crystal arthropathies are a diverse group of disorders characterized by deposition of various minerals in joints and soft tissues leading to inflammation. Clinical presentations of the different types of crystal arthritis are often characteristic enough to differentiate them from each other and other inflammatory arthropathies, but mistakes can be made, leading to delayed or incorrect management. Gout, the most common crystal arthropathy, is caused by monosodium urate crystal precipitation and appears to be increasing in clinical complexity and prevalence. In addition to gout, two other main crystal types are associated with inflammatory symptoms resulting from their deposition in and around joints. These are calcium pyrophosphate dihydrate, causing pseudogout, and basic calcium phosphate (BCP/hydroxyapatite). The most accurate way of diagnosing the common forms of crystal-associated arthritis is through the identification of specific crystals in synovial fluid. Crystal arthritis causes exquisite pain, and management is directed towards the control of acute flares, followed by prevention of recurrent episodes. Traditionally, the prophylaxis of gout has depended largely on the use of allopurinol, but newer drugs such as febuxostat are proving to be useful for those who cannot tolerate allopurinol. Better understanding of the pathophysiology of the disorder has led to the development of biologic treatments, which are showing promise as potential treatment strategies in resistant cases.