Localized retroperitoneal Rosai-Dorfman-Destombes disease as a cause of fever of unknown origin in adults. Case report and review of the literature

•The localized abdominal RDD could be a possible cause of FUO.•RDD should be considered in the differential diagnosis of localized retroperitoneal mass and FUO.•FDG-PET/CT is a useful diagnostic tool for initial diagnosis, staging, and follow-up.•In localized RDD, the surgery can be a definitive treatment.