Severe myopathy complicating multisystem inflammatory syndrome in adults (MIS-A) in a young man.

We report the case of a man in his early 30s who presented with high fever, cervical lymphadenopathy, maculopapular rash and considerably elevated inflammatory markers. Further evaluations revealed cardiomyopathy and renal failure. During hospitalisation he developed profound generalised muscle weakness caused by diffuse myopathy without elevated creatine kinase. He was eventually diagnosed with multisystem inflammatory syndrome in adults (MIS-A) after it was established that he had been suffering from COVID-19 5 weeks prior to presentation. He was started on intravenous immunoglobulins and high-dose corticosteroids, after which symptoms resolved rapidly. MIS-A is a rare but severe complication of COVID-19, whose pathogenesis is insufficiently understood. This case provides further insight into this new disease entity by describing a previously unreported disease progression with severe inflammatory myopathy without elevated creatine kinase.