[Periarthritis calcarea].

Over the past few years periarthritis calcarea - also known as hydroxyapatite rheumatism - has attracted increasing interest. The periarticular calcification hitherto regarded as a secondary finding is today a well-defined disease entity occurring either in localized or generalized form, i.e. around one or more joints respectively. Although the origin of this calcification is now known, various hypothetical causes have been discussed in the literature. In the light of studies on familial clustering and the HL-A constellation, it is now evident that genetic factors have a definite role to play in the etiology of the disease. Even though no metabolic defect has been identified as yet, it is impossible to state with certainty that no metabolic cause is involved. As in gout, periarthritis calcarea is liable to cause attacks of acute pain that last for several days and then disappear. In consequence, the clinical picture is misleadingly similar to that of arthritis. The subsequent disappearance of the periarticular calcium deposits previously shown to be present can be considered a cardinal symptom of the disease. To detect this calcification it is necessary to use the electron microscope, since the crystals are too small to be seen with the light microscope. Periarthritis calcarea undoubtedly ranks as a crystallopathy. Since its origin is unknown, causal therapy such as exists for gout cannot be adopted. Treatment is restricted to purely symptomatic measures.