While a majority of the focus in coronavirus disease 2019 (COVID-19) has been on the common and often fatal lung disease, reports of neurologic dysfunction have been increasing since the pandemic began.
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2 The spectrum of neurologic disease has been broad, from encephalopathy to thromboembolic disease,
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2 among a series of other pathologic mechanisms described by others.
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12 While these reports have not described serotonin syndrome-like manifestations per se, the evidence is mounting in regard to the presence of elevated plasma serotonin levels in COVID-19 patients,
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14 both in severe and non-severe disease, thought to be a result of an intense degree of platelet activation and serotonin liberation from activated platelets due to severe acute respiratory distress syndrome 2 (SARS-CoV-2) infection.
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16 Clinically, in two case series, more than 60% of severe COVID-19 subjects exhibited hyperreflexia or myoclonus,
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18 signs relatively specific for serotonin toxicity, occurring at a high enough rate in severe COVID-19 that is unaccountable for by pre-existing use of serotonergic medication. In addition, diarrhea of COVID-19 has also been attributed to an elevated plasma serotonin state.
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