A rare cause of proximal muscle weakness: immune necrotising myopathy

Background Immune-mediated necrotising myopathies are characterised clinically by the subacute onset of proximal limb weakness, accompanied by elevated creatinine kinase levels. They are distinguished from other myopathies by the absence of prominent infiltration of the muscle with inflammatory cells in the biopsies. Case presentation A 44-year-old man presented with upper extremity weakness and dysphagia. Laboratory tests included a creatinine kinase level of 4362 U/L (normal: 52-336 U/L). Rheumatological markers were all negative. A muscle biopsy showed multiple necrotic fibres with minimal inflammatory infiltration. One gram of methylprednisolone (IV) was given, followed by 1 mg/kg of methylprednisolone daily by the oral route. Intravenous immunoglobulin (0.4 mg/kg/day) was given for five days. Muscle weakness regressed and dysphagia disappeared with treatment. The patient remains well in the 23rd month of treatment, taking 5 mg/day prednisolone and monthly intravenous immunoglobulin. Conclusion Treatment of immune-mediated necrotising myopathy can be challenging as evidence-based therapeutic options are limited. It is generally accepted that early and extensive immunosuppression, including glucocorticoids as first-line agents, may be required.