[Monarthritis of unknown etiology: course and prognosis].

The diagnosis of monarthritis of unknown etiology is made by exclusion. Monarthropathies, periarthropathies, monarthritis of known etiology and systemic disease of which monarthritis is the first manifestation have to be excluded initially. Furthermore, during the course of the disease one has to look for initially undiagnosed causes of systemic diseases which are manifesting themselves during the course, such as rheumatoid arthritis, ankylosing spondylitis, sarcoidosis by repeated examination. After remission the diagnosis of monarthritis of unknown etiology can be made. There is, after a period of remission, rarely a relapse of the disease and transition into rheumatoid arthritis. There are four forms of monoarthritis of unknown aetiology, namely the acute form, the recurrent acute form, the persistent chronic form and the recurrent chronic form. According to the literature, monarthritis of unknown etiology resolves in about 70% of the cases after one year, in about 80% after two years and in about 90% after three years, in the great majority without leaving any signs of destruction. Non steroidal anti-inflammatory drugs, intra-articular corticosteroids, synovectomy or synoviorthesis can temporarily relieve symptoms and signs of inflammation. They have never proved to alter the course of the disease regardless of the length or the extent of the final clinical or radiological destruction. There are no prognostic markers for length and severity of the disease. As monarthritis of unknown aetiology is a self-limiting disease without destruction, it is also called benign monarthritis.