Severe Serotonin Syndrome under Duloxetine in a Patient with Coeliac Disease — is There a Connection? A Case Report

Background and objectives: Serotonin Syndrome (SS) is a rare but severe drug side effect of serotonergic substances. The various symptoms of SS are the result of excess serotonin on the central and enteric nervous system. Monotherapy with serotonin-norepinephrine reuptake inhibitors (SNRIs) like duloxetine induce the syndrome very rarely. It has been shown that patients with coeliac disease (CD) per se have significantly increased serum serotonin levels. Methods: We report the case of a 41-year-old white male who developed an unusual severe SS under monotherapy with duloxetine. Remarkably, the patient was also diagnosed with CD shortly before. Results: After all other possible causes have been excluded by intensive diagnostics the clinical diagnosis of a serotonergic syndrome was made. Conclusion: To our knowledge, this case is the first report of such a severe serotonin syndrome under duloxetine monotherapy, which might be boosted trough the patient's coeliac disease. We suspect that the serotonin level of the patient could already have been significantly increased due to his CD and therefore jointly responsible for the fulminant serotonin syndrome under duloxetine. (C) 2020 Asociacion Universitaria de Zaragoza para el Progreso de la Psiquiatria y la Salud Mental. Published by Elsevier Espana, S.L.U. All rights reserved.