Immune-mediated necrotizing myopathy is a rare autoimmune myopathy that can be seen with statin exposure, with characteristically rapidly progressive proximal muscle weakness. Here, we presented a severe case of a 70-year-old female who presented for rapidly progressive proximal muscle weakness that acutely progressed in the setting of increased dosage of statin, later complicated by bronchoscopy-confirmed alveolar hemorrhage. While extramuscular involvement is uncommon, pulmonary manifestations typically manifest as ILD, particularly in anti-SRP associated disease. Rarely, this can cause a rare but serious complication, diffuse alveolar hemorrhage (DAH).

A 70-year-old female with history of ILD presented with rapidly progressive generalized weakness and myalgias. Neurologic examination revealed symmetric proximal greater than distal weakness (LE > UE) and bilateral Babinski signs, raising concern for a myopathic process with possible central involvement.

Laboratory evaluation demonstrated severe rhabdomyolysis (CPK ~28,000 U/L), AKI (creatinine >5), and transaminitis. Further history identified recent up-titration of atorvastatin. Myopathy was confirmed after a left quadriceps biopsy, which suggested immune-mediated necrotizing myopathy. The patient was treated with IVIG and statin therapy was discontinued.

Despite immunotherapy, the patient developed progressive bulbar weakness with dysphagia and aspiration, followed by acute hypoxic respiratory failure requiring intubation. Bronchoscopy confirmed diffuse alveolar hemorrhage. Treatment was expanded to IV corticosteroids and rituximab. Her course progressed to severe ARDS with refractory hypoxemia despite maximal supportive care.

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This case reviews the presentation of immune-mediated necrotizing myopathy, which includes a clinical history of subacute progressive proximal weakness with profound creatine kinase elevation, highlighting the importance of early neurologic involvement guiding diagnosis and immunotherapy. Rare complications include DAH, which can present as a catastrophic extramuscular manifestation of autoimmune myopathy. The pathophysiology may involve immune-mediated vascular injury, though mechanisms remain poorly understood. Early, aggressive immunotherapy—including IVIG, corticosteroids, and B-cell depletion—is recommended, but outcomes in severe systemic disease remain poor.