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

Abstract

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 ofmononuclear or polymorphonuclear cells around ≤ 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 fibrinold 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 ≤ 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 interobserver concordance on the presence of fibrinoid necrosis and of PVIs with ≤ three cell layers. Conclusions - The assessment of PVIs with ≤ 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 ≤ three cell layers is more sensitive than that of fibrinoid necrosis in the diagnosis of RV.