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.