Immune myopathies with perimysial pathology: Clinical and laboratory features

Objective Immune myopathies with perimysial pathology (IMPP) have a combination of damage to perimysial connective tissue and muscle fiber necrosis, more prominent near the perimysium. We studied the clinical and laboratory correlates of patients with pathologically defined IMPP. Methods This is a retrospective chart and pathology review of 57 consecutive patients with IMPP myopathology and, for comparison, 20 patients with dermatomyositis with vascular pathology (DM-VP). Results Compared with DM-VP, IMPP patients more commonly had interstitial lung disease (ILD) (p < 0.01), Raynaud phenomenon (p < 0.05), mechanic's hands (p < 0.05), arthralgias (p < 0.001), and a sustained response to immunomodulatory therapy (p < 0.05), and less frequently had a concurrent malignancy (p < 0.01). IMPP patients had higher serum creatine kinase values (p < 0.05), more frequent serum Jo-1 (p < 0.03) or SSA/SSA52 autoantibodies (p < 0.05), and less frequent antinuclear antibodies (p < 0.01). IMPP patients with serum Jo-1/antisynthetase antibodies were more likely to have ILD (p < 0.05) and inflammatory arthritis (p < 0.05) than IMPP patients without these antibodies. Conclusions IMPP myopathology is associated with an increased risk of ILD, Raynaud phenomenon, mechanic's hands, and inflammatory arthritis when compared with another immune myopathy (DM-VP). IMPP patients require regular screening for ILD, particularly those with antisynthetase antibodies. The absence of myositis-specific autoantibodies in a large percentage of IMPP patients emphasizes the important role for myopathology in identifying patients at higher risk of severe comorbid conditions such as ILD.