The diagnostic value of perivascular infiltrates in muscle biopsy specimens for the assessment of rheumatoid vasculitis.

OBJECTIVE To determine the diagnostic value of perivascular infiltrates (PVI) in randomly obtained muscle biopsy specimens for the assessment of rheumatoid vasculitis (RV). METHODS The number and size of PVIs, defined as the presence of mononuclear or polymorphonuclear cells around > or = 50% of the circumference of a vessel wall, as well as the presence of fibrinoid necrosis were determined in frozen sections of muscle samples of RV patients with histologically confirmed vasculitis in fixed muscle tissue (n = 12). The findings were compared with those observed in frozen sections of muscle biopsy specimens of rheumatoid arthritis (RA) patients not suspected of vasculitis (n = 14) and patients with osteoarthritis (OA) (n = 11). The presence of PVIs and of fibrinoid necrosis were sought in four frozen sections of the muscle biopsy specimen. RESULTS PVIs were observed in 75% of the RV patients, which was significantly (p < 0.05) higher than the frequency found in RA (14%) or OA (18%) patients. PVIs with > or = three cell layers were found in 67% of the RV patients and in none of the RA and OA patients (p < 0.05). Fibrinoid necrosis was found in least one of four frozen section in 33% of the RV patients. There was a good intra-observer and inter-observer concordance on the presence of fibrinoid necrosis and of PVIs with > or = three cell layers. CONCLUSIONS The assessment of PVIs with > or = three cell layers in a muscle biopsy specimen is a specific and reliable test in discriminating RV from RA without vasculitis. The demonstration in muscle of PVIs with > or = three cell layers is more sensitive than that of fibrinoid necrosis in the diagnosis of RV.