SHM Converge Scientific Abstract ePoster Gallery-Immune Mediated Necrotizing Myopathy Presenting With Cardiogenic Shock

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This case report describes immune-mediated necrotizing myopathy (IMNM), a rare inflammatory muscle disease, in a 38-year-old woman who presented with one month of progressive weakness that worsened to involve the shoulders, hands, feet, dysarthria, and shortness of breath. On arrival, she was critically ill with hypoxia, hypotension, and tachycardia, and labs showed markedly elevated creatine kinase, troponin, aldolase, and NT-proBNP, suggesting severe muscle injury and cardiac involvement.<br /><br />She required intubation for impending respiratory failure and briefly experienced cardiac arrest. Echocardiography and hemodynamic monitoring showed reduced cardiac function and low cardiac output, requiring inotropic support with milrinone after inadequate response to vasopressors. She was treated with high-dose methylprednisolone, followed by mycophenolate mofetil and a prednisone taper. Autoimmune testing was negative for anti-HMGCR and anti-SRP antibodies, leading to a diagnosis of antibody-negative IMNM. MRI of the thighs showed diffuse muscle edema consistent with myositis, and muscle biopsy confirmed necrotizing myopathy with MHC class I positivity.<br /><br />Her cardiac function and muscle strength gradually improved with immunosuppressive therapy, allowing discontinuation of milrinone and ventilatory support. She is now ambulatory, though she still has foot drop.<br /><br />The discussion notes that IMNM is characterized by progressive proximal weakness and muscle fiber necrosis with little lymphocytic infiltration. While anti-HMGCR and anti-SRP antibodies are typical, antibody-negative cases also occur. Cardiac involvement can include myocarditis, arrhythmias, and heart failure, but overt cardiogenic shock is very rare, especially in antibody-negative IMNM. This case is presented as the first reported example of antibody-negative IMNM causing cardiogenic shock that improved with immunosuppression.

Asset Subtitle

Arkaketan Chatterjee

Meta Tag

Author List Arkaketan Chatterjee, Farzane Saeidifard, Mariam Ansar, Rohan Bhan, Sima Terebelo, Stephanie Ogbonda

Category Clinical Vignettes

Concept Immune-Mediated Necrotizing Myopathy

Concept Proximal Weakness

Concept Muscle Enzyme

Concept Muscle Biopsy

Concept Autoimmune Antibody Testing

Distinguished Non-Finalist

Presenter Organization Brookdale University Hospital Medical Center, New York

Presenting Author Arkaketan Chatterjee

Track Adult

Keywords

immune-mediated necrotizing myopathy

IMNM

antibody-negative myopathy

cardiogenic shock

myocardial involvement

proximal muscle weakness

elevated creatine kinase

muscle biopsy

myositis

immunosuppressive therapy

Immune-Mediated Necrotizing Myopathy

Proximal Weakness

Muscle Enzyme

Muscle Biopsy

Autoimmune Antibody Testing