Steroid-Responsive Seronegative Immune-Mediated Necrotizing Myopathy Likely Triggered by Coxsackie B Virus: A Case Report

Viral myositis can be mistaken for other types of myopathies, and the main causes of muscle damage are direct myotoxic effect and immune-mediated mechanisms. The biochemical parameters, electromyography (EMG), and muscle biopsy findings can be similar in viral myositis and idiopathic inflammatory myopathies. Viruses are rarely isolated from muscle biopsy specimens, so clinical evaluation and ancillary tests are necessary for a definitive diagnosis. Viral etiology is suspected when weakness occurs after a respiratory or gastrointestinal infection. Coxsackieviruses, particularly A9 and B5, can cause myositis and muscle necrosis. This is a case of a 47-year-old female with a history of alcoholic cirrhosis and a recent coxsackie B virus infection presented with weakness, numbness, and body pain. Creatine kinase levels were elevated but tests for extended myositis panel and antibodies were negative. A muscle biopsy revealed immune-mediated inflammatory myopathy. After a week without improvement, the patient received IV methylprednisolone followed by prednisone taper leading to improvement in symptoms. Prolonged myalgia has been observed in patients recovering from coxsackie A infections. The role of coxsackie B in causing myositis is still disputed and requires more reported data and guidelines. Clinicians should consider testing for coxsackie B as a potential cause of weakness. Awareness of potential complications like myositis can aid in effective patient management. More cases are needed to determine the significance of steroid use in managing coxsackie B-related muscle weakness.