Acute flaccid myelitis (AFM) is characterized by flaccid paralysis of one or more limbs, often following a viral illness, with magnetic resonance imaging findings consistent with inflammation of the spinal cord gray matter. It is unclear whether all patients with AFM will have full recovery of neurologic function. Since 2014, there have been several clusters of AFM in the United States, with a 3-fold increase in reported AFM cases recorded in 2018 compared with the previous year. Epidemiological evidence supports a temporal association between respiratory enteroviral illness, particularly with enteroviruses D68 and A71, and clustering of AFM cases. However, causality has yet to be established. Treatment of AFM is primarily supportive. Adjunctive therapies such as intravenous immunoglobulin, corticosteroids, plasmapheresis, and fluoxetine have not been found to improve long-term outcomes. Further research is urgently needed to characterize and optimize management of this emerging, yet poorly understood, condition.
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