Respiratory failure as presenting symptom of necrotizing autoimmune myopathy with anti-melanoma differentiation-associated gene 5 antibodies

Necrotizing autoimmune myopathy (NAM) is a rare variant of idiopathic inflammatory myopathies associated with various underlying conditions. We describe a 48-year-old woman with a history of breast cancer who presented with acute respiratory failure and progressive loss of strength in her limb muscles over a period of two months. Muscle biopsy was consistent with necrotizing myopathy. No signs of active tumour were found. Immunoblot was positive for anti-melanoma differentiation-associated gene 5 (MDA5) antibodies. Based on the subacute onset and muscle biopsy a diagnosis of NAM was made. Treatment with immunosuppressive and immunomodulating therapy led to almost complete recovery. Respiratory insufficiency as a presenting symptom of NAM is unusual. Recognition of this manifestation is crucial as early and aggressive treatment can lead to substantial recovery.