Gastric herpes simplex virus type 1 infection is associated with functional gastrointestinal disorders in the presence and absence of comorbid fibromyalgia: a pilot case–control study

PURPOSE: Animal studies have linked gastric herpesvirus infections to symptoms associated with functional gastrointestinal disorders (FGIDs). Herpesviruses have also been hypothesized to contribute to fibromyalgia (FM), a chronic pain syndrome frequently comorbid with FGIDs. The purpose of this study was to compare the prevalence of gastric herpesvirus infection in patients with FGIDs, with and without comorbid FM, to that of controls. METHODS: For this pilot case–control study, we enrolled 30 patients who met both the Rome IV diagnostic criteria for one or more FGIDs and the American College of Rheumatology 2010 criteria for FM, 15 patients with one or more FGIDs without comorbid FM, and 15 control patients. Following endoscopic examination, gastric biopsies were analyzed for herpesvirus DNA and protein, Helicobacter pylori infection, and histological evidence of gastritis. Importantly, the viral nonstructural protein ICP8 was used as a marker to differentiate cell-associated actively replicating virus from latent infection and/or free virus passing through the GI tract. RESULTS: Gastric herpes simplex virus type 1 (HSV-1) infection, as indicated by ICP8 presence, was significantly associated with FGIDs in the presence (OR 70.00, 95% CI 7.42–660.50; P < .001) and absence (OR 38.50, 95% CI 3.75–395.40; P < .001) of comorbid FM. Neither histological gastritis nor H. pylori infection were found to be associated with FGIDs or FM. CONCLUSIONS: HSV-1 infection was identified in gastric mucosal biopsies from patients with diverse FGIDs, with and without comorbid FM. Larger, multi-center studies investigating the prevalence of this association are warranted. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s15010-022-01823-w.