http://repub.eur.nl/res/aut/2359/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/8508/ 2005-01-01T00:00:00Z BACKGROUND: Pigmented villonodular synovitis (PVNS) is considered to be a neoplastic-like disorder of the synovium histologically characterised by villonodular hyperplasia, resulting in dense fibrosis and haemosiderin deposition. The pathogenesis of the disease is still unknown. CASE REPORT: A patient presented with severe treatment resistant PVNS of the right knee joint. Several conventional treatment regimens, including open surgical synovectomy and intra-articular injections of yttrium-90 ((90)Y) failed to control the disease. After finding marked tumour necrosis factor alpha (TNF alpha) expression in arthroscopic synovial tissue samples, treatment with an anti-TNF alpha monoclonal antibody (infliximab) at a dose of 5 mg/kg was started. Additional courses with the same dose given 2, 6, 14, and 20 weeks later, and bimonthly thereafter up to 54 weeks, controlled the signs and symptoms. Immunohistological analysis at follow up identified a marked reduction in macrophage numbers and TNF alpha expression in the synovium. DISCUSSION: This is probably the first case which describes treatment with TNF alpha blockade of PVNS in a patient who is refractory to conventional treatment. It provides the rationale for larger controlled studies to elucidate further the efficacy of TNFalpha blockade treatment in refractory PVNS.