Among 1400 muscle biopsies, we found 16 cases with rimmed vacuoles whose diagnosis were sporadic inclusion body myositis (IBM) (4 cases), juvenile spinal muscular atrophy (6 cases), distal myopathies (3 cases), limb-girdle muscular dystrophy (2 cases), and peripheral neuropathy (1 case). Monoclonal antibodies reactive for T lymphocytes and subsets, B lymphocytes, macrophages, natural killer cells, immunoglobulins, and complement were used to analyze the inflammatory infiltrate. The analysis was quantitative and according to the site of accumulation (interstitial, endomysial, and perivascular). The immunocytochemical analysis showed CD8+ lymphocytes in the interstitial in most cases, occasionally inside of muscle fibers, and rarely in the perivascular region. The IBM cases had an increased number of CD8+ lymphocytes comparing with the other diseases. CD8+/CD4+ ratio was increased in IBM compared with the other diseases. Macrophages were frequent in IBM, distal myopathy, and one case of limb-girdle muscular dystrophy. Natural killer cells were frequent at interstitial site in IBM but rare in the other diseases. Immunoglobulins and complement deposition were slightly more intense in IBM than in the other diseases. The case of peripheral neuropathy had no cells or immunoglobulins deposition. The increased number of CD8+ lymphocytes and the CD8+/CD4+ ratio help to distinguish IBM from other neuromuscular disorders with rimmed vacuoles.
immunocytochemistry; rimmed vacuoles; cytoplasmic inclusion; inclusion body myositis; juvenile spinal muscular atrophy; distal myopathies; limb-girdle muscular dystrophy
