Pigmented Villonodular Synovitis Developing in the Knee of a Rheumatoid Arthritis Patient Mistaken as a Rheumatoid Arthritis Flare-Up / 대한내과학회지

ABSTRACT

Pigmented villonodular synovitis is a benign tumor arising from synovial fibroblasts or histiocytes. There are diffuse and localized forms: the former involves the entire synovium and the latter consists of nodules, small tumefactions, or pedunculated masses. The knee is the joint most commonly affected and the clinical diagnosis is difficult, so initial misdiagnosis is common. We report a case of pigmented villonodular synovitis developing in the knee of rheumatoid arthritis (RA) patient, mistaken for an RA flare-up.