IntroductionAcute abdomen and acute appendicitis are unusual clinical presentations that occur in dengue infection–caused illness. Lymphoid hyperplasia and mesenteric adenitis are possible explanations, although vasculitis in the pathology of dengue infection has not been reported. Authors of previous case reports have described mimicking of acute appendicitis discovered upon surgical treatment. Dengue virus has not been proven to cause acute appendicitis.Case presentationWe report a case of an 8-year-old Sinhalese boy who developed acute appendicitis during the acute phase of serologically confirmed dengue fever. Although abdominal pain, vomiting and right-sided tenderness were present at the time of admission, a diagnosis of acute appendicitis was considered only 18 hours later, when abdominal guarding and a well-defined mass in the right iliac fossa were detected clinically and ultrasonographically. Conservative management with intravenous antibiotics was successful.ConclusionIn areas where dengue is endemic, awareness of dengue viral infection as a non-surgical cause of acute abdomen, as well as its ability to mimic acute appendicitis, is important because unnecessary surgery-related morbidity can be decreased. However, delaying or missing the diagnosis of acute appendicitis can result in serious complications. This message is particularly relevant to clinicians, especially pediatricians and surgeons, who encounter large numbers of patients during dengue epidemics and run the risk of missing the diagnosis of acute appendicitis. Likewise, delaying or missing the diagnosis of dengue hemorrhagic fever can lead to dengue shock syndrome and even death. This case highlights the need for careful evaluation of each patient who presents with acute abdomen and dengue infection.