Multiple extra-articular synovial cyst formation: case report and review of the literature

To investigate the clinical manifestations and the treatment strategy of a very rare entity of disease manifesting as multiple extra-articular cystic synovitis with recurrent polyarthralgia.

A 47 year old male patient with multiple extra-articular synovial cysts was followed up prospectively for 13 years. The clinical manifestations and response to various treatments were recorded. Comparisons are made among the five reported cases (including the present case).

Multiple synovial cysts over the tendon sheath and bursae appeared successively with and without antecedent growth of nodules during 13 years of follow up. Although polyarthralgia and high titred rheumatoid factor persisted throughout the course, there were no roentgenographical changes of joints specific to rheumatoid arthritis (RA). The synovial cysts and arthralgia failed to respond to any of the disease modifying anti-rheumatic drugs (DMARDs) prescribed. Systemic involvements such as pulmonary interstitial fibrosis and skin ulcers were also noted, but they were not progressive.

Multiple extra-articular cystic synovitis is an uncommon disease entity closely related to RA. It has been reported exclusively in Japanese subjects and therefore some cultural factors, either genetic or environmental, may contribute to its development.