A33-44 Unmasking A Possible Malignancy: Necrotizing Myopathy With Refractory Respiratory Failure

Abstract Background Immune-mediated necrotizing myopathy (IMNM) is a rare inflammatory myopathy characterized by severe proximal weakness and markedly elevated creatine kinase. Respiratory muscle involvement requiring invasive mechanical ventilation is uncommon and poses major weaning challenges. Case Presentation A 62-year-old woman with type 2 diabetes presented with progressive limb weakness, dysphagia, and diffuse rash (Left image). Laboratory evaluation showed creatine kinase ∼8,000 U/L and nephrotic-range proteinuria with 24-hour urine total protein 4.1 g/day. Electromyography demonstrated irritable myopathy, and muscle biopsy on hospital day (HD) 3 confirmed necrotizing myopathy with denervation atrophy. A comprehensive serologic panel including ANCA/MPO/PR3, ANA, myositis-specific antibodies, HIV, hepatitis B/C, and syphilis was negative. She received IVIG and pulse methylprednisolone followed by taper. On HD 5, she developed acute hypoxic respiratory failure requiring intubation, with persistent ventilator dependence leading to tracheostomy on HD 12 due to profound diaphragmatic weakness. Her course was complicated by ventilator-associated pneumonia and severe anasarca, necessitating continuation of intravenous steroids. Despite biochemical improvement with CK normalization by HD 18, she remained clinically weak. CT imaging on HD 19 revealed a hypoenhancing cervical mass with endometrial cavity distention (Right image). Gynecologic oncology evaluation considered these findings suspicious for FIGO stage IB2 cervical malignancy, but the patient declined pelvic examination and biopsy. Given concern for a potential paraneoplastic IMNM and inability to confirm malignancy, Corticosteroids were cautiously tapered beginning HD 21. By HD 23, she tolerated a capped tracheostomy but remained too weak for ventilator liberation. Palliative care was engaged to support shared decision-making. Discussion This case highlights a rare manifestation of IMNM with severe respiratory muscle involvement, leading to prolonged mechanical ventilation and difficult weaning. Management was further challenged by suspected but unconfirmed malignancy limiting immunosuppression. Early multidisciplinary involvement is crucial when respiratory failure complicates IMNM. Conclusion Seronegative IMNM can present with life-threatening diaphragmatic dysfunction. Recognition of prolonged ventilatory dependence as a clinical phenotype should prompt malignancy evaluation and coordinated management. This abstract is funded by: none