A Case of Viral Myositis Simulating Polymyositis

Background: Acute viral myositis is a rare condition that may occur even during the recovery phase of an illness. The disease is characterized by myalgia and proximal weakness, with an isolated laboratory finding of elevated serum creatine kinase (CK). We report a case of a 72-year-old female who presented with proximal muscle weakness and myalgia three weeks after an episode of fever. Objective: The aim was to report a rare cause of myositis caused by viruses that simulate polymyositis. Methods: A thorough clinical, laboratory, and electrophysiological evaluation was done. The initial CPK was very high, 17,493 U/L. The nerve conduction study was normal, and needle EMG showed some features of denervation with myopathic MUAPs. Histopathological findings were also suggestive of inflammatory myopathy. Both anti-cytomegalovirus-IgM and IgG were positive. Result: The condition simulating polymyositis both clinically, biochemically, electrophysiologically, and also histopathologically. However, the patient improved rapidly over a short period with normalization of CPK without any corticosteroid or immunosuppressive treatment. Based on the above features and the self-limiting nature of the disease, the patient was diagnosed as a case of Cytomegalo virus viral myositis. Conclusion: Viral myositis is a self-limiting myopathy that mimics polymyositis as both having similar clinical and laboratory features. However early differentiation is important because viral myositis recovers spontaneously whereas polymyositis needs aggressive treatment with high-dose corticosteroids and immunosuppressants. Though not common early diagnosis of viral myositis if possible can reduce the hazard of long-term use of these drugs. Bangladesh Med Res Counc Bull 2024; 50: 155-158