Myositis Due to Parvovirus B19: A Case Report and Literature Review.

Myositis is a condition characterized by muscle inflammation due to multiple etiologies, including autoimmune disease, medication, and infection. Viral myositis is most frequently seen in children after influenza infection, but Parvovirus B19 has also rarely been associated with myositis. We report the case of a 42-year-old male with a medical history of low back pain due to spondylosis who presented to the hospital with a one-month history of bilateral thigh and calf pain associated with subjective weakness and a one-week history of fevers. His wife and son were diagnosed with Parvovirus B19 infection one month before his symptoms began. The physical exam was notable for prominent tenderness to palpation of the anterior thigh muscles and calves and mild swelling around the ankles without intra-articular effusion. Strength was normal in all extremities. Lower extremity MRI revealed extensive multifocal, patchy, and feathery edema throughout the lower extremities. Aldolase, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and Parvovirus B19 serum IgM were elevated, but creatine kinase, extended myositis antibody panel, and 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase antibody were normal. A vastus lateralis muscle biopsy demonstrated mild acute myopathic changes with patchy upregulation of major histocompatibility complex (MHC) class I antigens. Parvovirus B19 polymerase chain reaction (PCR) on the muscle tissue was positive. The patient was diagnosed with myositis due to Parvovirus B19 infection and started on scheduled naproxen. Five months later, his symptoms had completely resolved, and he no longer required naproxen. A literature review of PubMed, Ovid, Scopus, Web of Science, and Cochrane databases for English-language articles using the search terms "idiopathic inflammatory myopathy" OR "myositis" OR "inflammatory myopathy" OR "dermatomyositis" OR "polymyositis" AND "Parvovirus B19" OR "parvovirus" revealed six other cases of myositis associated with Parvovirus B19 infections, although two of the six cases had characteristics of dermatomyositis rather than viral myositis. Aside from the patient with dermatomyositis, one other patient had a muscle biopsy with positive Parvovirus B19 testing. To our knowledge, our case is the second description of biopsy-proven Parvovirus B19 myositis, and the first to describe specific histopathology. Further, ours is the first case of biopsy-proven Parvovirus B19 myositis to be successfully treated with non-steroidal anti-inflammatory drugs (NSAIDs) in an adult.