Objective: Histological analysis of random quadriceps muscle biopsy specimens can be used to detect vasculitis in patients with rheumatoid arthritis (RA). This study aimed at determining the immunohistological features in patients with clinical suspicion of rheumatoid vasculitis, but without a transmural infiltrate or fibrinoid necrosis of the vessel wall on routine histology.
Methods: Three groups of patients with RA were studied: (a) without clinical signs of vasculitis (n=6); (b) with recent onset of extra-articular features and a clinical suspicion of vasculitis but normal routine histology (n=11); and (c) with recent onset of extra-articular features and vasculitis, histologically proved either in muscle or other biopsy specimens (n=14). A control group of patients with osteoarthritis was also included (n=5). Frozen sections from quadriceps muscle biopsy specimens were analysed with monoclonal antibodies to detect CD3, CD4, CD8, CD68, ICAM-1, VCAM-1, and HLA-DR. The slides were evaluated using a semiquantitative scoring system (0-4).
Results: The mean scores gradually increased from group 1 to 3, leading to significant differences between groups 1 and 2, but not between groups 2 and 3 for most markers (p< 0.05). Thus the pathological changes were similar for the two groups with clinical signs of vasculitis, even when the conventional histological evaluation was negative. Higher immunohistological scores were associated with perivascular infiltrates on routine histology.
Conclusion: The pathophysiological events leading to vasculitis are reflected by the changes in the quadriceps muscle biopsy specimens. The data indicate that the sensitivity of examination of muscle biopsy specimens for the diagnosis of rheumatoid vasculitis can be increased by the use of new criteria.