– Necrotizing polymyositis – a case report

Objective: Autoimmune neuromuscular disorders as polymyositis (PM) are rare and heterogeneous conditions. PM and its variant necrotizing PM (nPM) are idiopathic inflammatory myositides similar as dermatomyositis and inclusion body myositis. Due to their rare occurrence, evidence based therapy regimens are lacking.

Methods: A case report of nPM and its successful treatment are presented. The diagnostic procedures including muscle biopsy, muscle MRI, electromyography and differenzial diagnosis are depicted, the therapeutic approaches of acute and long-term treatment decisions discussed.

Results/Case report: A 47-year old patient presented rapidly evolving muscular weakness and loss of weight over a course of 3 months with elevated creatine kinase (CK) levels with a peak of 26,000U/l.

Screening for systemic autoimmune, neoplastic and infectious disorders was negative.

Electromyography revealed acute denervation and severe myopathic changes in both M. biceps brachii and M. rectus femoris.

The MRI scan of the right arm revealed diffuse muscle edema with gadolinium enhancement pronounced in the proximal arm and shoulder girdle muscles, consistent with severe myositis.

Muscle biopsy of the right deltoid muscle showed scattered necrotic fibres and regenerating fibres and only few inflammatory infiltration of the endomysium. These light-microscopic findings were indicative of a necrotizing myopathy.

Immunohistochemical staining revealed diffuse upregulation of MHC1 and some CD3-positive T-lymphocytes in the endomysium and many CD68-positive macrophages, but unremarkable MAC staining without pericapillary accumulation of C5b-9.

Supported by these findings, nPM was diagnosed.

Corticosteroid pulse therapy led to marked decrease in CK levels, but failed to induce symptomatic improvement. In turn, further escalating treatment by plasmapheresis and IVIG therapy was performed.

For further stabilization, a multimodal immunotherapeutic regimen with cyclophosphamide induction therapy and de-escalation to azathioprine/ciclosporin co-therapy was applied leading to complete remission with enduring therapeutic effect.

Conclusion: Long-term immunosuppression after efficient crisis intervention seems to be crucial for prevention of a relapse of acute inflammatory myopathy. Therapeutic approaches are still mainly based on clinical experience rather than evidence based data as results of controlled trials are lacking. Therefore, therapeutic considerations have to be discussed individually.