COVID-19-Associated MDA5-Mediated Necrotizing Myositis

Area of Science:

• Neurology
• Immunology
• Infectious Diseases

Background:

• Rhabdomyolysis and autoimmune myopathies share symptoms like muscle pain and weakness, complicating diagnosis.
• The SARS-CoV-2 pandemic has seen a rise in reported autoimmune myositis cases.
• Distinguishing viral-induced muscle damage from autoimmune conditions is clinically challenging.

Purpose of the Study:

• To report the first case of melanoma differentiation-associated gene 5 (MDA5)-associated necrotizing myositis following SARS-CoV-2 infection.
• To highlight a unique presentation of COVID-19-related myopathy without typical skin or lung involvement.
• To emphasize the diagnostic challenges and treatment response in post-viral autoimmune myopathies.

Main Methods:

• Clinical case presentation of a young African American male with post-SARS-CoV-2 myopathy.
• Diagnostic workup including serum creatine kinase (CK) levels, inflammatory markers, autoimmune panel, and chest CT.
• Treatment assessment with intravenous fluids and empiric steroid therapy.
• Confirmation via muscle biopsy and specific antibody testing (MDA5).

Main Results:

• Patient presented with severe myalgias and weakness post-COVID-19, with markedly elevated CK levels (>300,000 U/L).
• Initial treatment for rhabdomyolysis yielded poor results, but empiric steroids led to rapid symptom and CK level improvement.
• Muscle biopsy confirmed necrotizing myositis, and elevated MDA5 antibodies were detected.
• The patient lacked typical MDA5-related skin and interstitial lung disease manifestations.

Conclusions:

• This is the first reported case of MDA5-associated necrotizing myositis triggered by SARS-CoV-2 infection.
• The absence of characteristic skin and lung findings in this patient broadens the clinical spectrum of MDA5 myositis.
• Further research is essential to understand COVID-19's role in autoimmune myopathies and develop targeted treatments.