Abstract

Objective: To describe isolated knee monoarthritis as a paraneoplastic syndrome heralding non-small cell lung cancer (NSCLC), and to discuss its clinical characteristics.

Methods: We reviewed the clinical records of all consecutive, new outpatients with isolated knee monoarthritis observed from January 2000 to December 2005. A systematic review of Medline and Cochrane Library databases was performed to identify English-language articles related to rheumatologic paraneoplastic syndromes associated with NSCLC.

Results: Over 6 years, we observed 6654 new outpatients with different rheumatic disorders. Of these, 296 (4.4%) presented with isolated monoarthritis of the knee. In 5 out of 296 (1.7%) patients this feature represented the initial manifestation of NSCLC. All 5 patients were middle aged males, with a long history of heavy cigarette smoking, who had a nonerosive, isolated knee monoarthritis, with mild articular fluid collection of non inflammatory type. NSCLC was resectable in all patients, and knee monoarthritis remitted with no relapse confirming its paraneoplastic nature. All 5 patients are in good condition after a median follow up of 41 months. The literature review revealed that paraneoplastic knee monoarthritis has not been previously reported.

Conclusion: Knee monoarthritis may represent in some cases a paraneoplastic syndrome heralding NSCLC in an early stage.