Abstract Details

Title Necrotizing Autoimmune Myopathy Associated With Anti-HMGCR Antibodies and Ductal Breast Carcinoma: A Case Report

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P8 - Poster Session 8 (11:45 AM-12:45 PM)

Poster/Presentation
Number 9-020

Objective NA

Background Necrotizing autoimmune myopathies are a subgroup of inflammatory myopathies characterized by proximal muscle weakness, markedly elevated creatine phosphokinase (CPK) levels, and muscle fiber necrosis with minimal inflammatory infiltrate. They are commonly associated with specific autoantibodies, such as anti-SRP or anti-HMGCR, and some cases have been linked to paraneoplastic syndromes.

Design/Methods Case presentation:
An 83-year-old woman with a medical history of hypertension, type 2 diabetes mellitus, and atorvastatin use presented with progressive proximal muscle weakness, dysphagia, and dyspnea. On hospital admission, elevated muscle and liver enzyme levels were documented: CPK (14,613 U/L), LDH, AST, and ALT. Myositis-specific autoantibodies were negative except for anti-PL-12 and anti-TIF1-γ (reported as indeterminate), with a positive anti-HMGCR antibody. Electromyography demonstrated findings consistent with a moderate chronic myopathy. Muscle biopsy revealed extensive muscle fiber necrosis without inflammatory infiltrate. Early discontinuation of statin therapy and initial treatment did not result in clinical improvement, raising suspicion for a paraneoplastic component. Whole-body computed tomography identified a left breast mass, subsequently confirmed by contrast-enhanced magnetic resonance imaging. Histopathological analysis revealed infiltrating ductal carcinoma with positive hormone receptors (ER+/PR+) and negative HER2 status.

Results

Treatment and outcome:
Immunosuppressive therapy was initiated with methylprednisolone, mycophenolate mofetil, and methotrexate, with abatacept administered during the perioperative period for left mastectomy. The patient showed marked clinical improvement, with a progressive decline in serum CPK levels to 584 U/L and gradual functional recovery.

Conclusions

This case highlights the importance of considering anti-HMGCR necrotizing myopathy potentially associated with neoplasms in patients who do not improve after initial treatment or statin discontinuation. A comprehensive approach, including immunomodulatory and oncologic therapy, proved effective, and close monitoring of muscle biomarkers was essential to assess therapeutic response.

Authors/Disclosures
Erick Alejandro Barajas Llamas, MD PRESENTER	Dr. Barajas Llamas has nothing to disclose.
Karen I. Pozo, MBBS	Dr. Pozo has nothing to disclose.
Kenny P. Gonzalez Aguilar, MD	Dr. Gonzalez Aguilar has nothing to disclose.
Leonel Cantu-Martinez, MD	Dr. Cantu-Martinez has nothing to disclose.
Jaime Javier Cantu Pompa, MD	Dr. Cantu Pompa has nothing to disclose.
Francys Romina Moreno Rodríguez, MD	Dr. Moreno Rodríguez has nothing to disclose.

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