Clinicopathologic characteristics of polymyositis patients with numerous tissue eosinophils

We evaluated associated clinicopathologic features of polymyositis (PM) patients with numerous tissue eosinophils.

680 muscle biopsies were examined in our institution and eight were identified with greater than 0.3 eosinophils per square millimeter in the inflammatory infiltrate without concomitant peripheral eosinophilia.

All eight patients had typical PM, but neither dermatomyositis nor inclusion body myositis was identified. Clinically, a large number of PM patients with eosinophils manifested an acute- or subacute-onset of symptoms, myoglobinuria, a marked elevation of serum creatine kinase, a good response to steroid therapy, and a relatively benign course compared with 26 PM patients without eosinophils. Muscle biopsies demonstrated necrotic fibers more frequently in PM patients with eosinophils than in PM patients without eosinophils. Hypertrophic fibers, fiber splitting, basophilic fibers, and lobulated fibers were less frequently observed in PM patients with eosinophils.

These results suggest that the majority of PM patients with eosinophils may be steroid-responsive and suffer an acute or subacute onset of PM.