Reye-like syndrome is a rare but potentially fatal pediatric disorder characterized by acute non-inflammatory encephalopathy and hepatic microvesicular steatosis. We report the sudden unexpected death of a previously healthy 6-year-old boy following a febrile viral-like illness with recurrent seizures, rapid neurological deterioration, and deep coma. Premortem investigations showed elevated liver transaminases, marked hyperammonemia, and hypoglycemia. Brain magnetic resonance imaging demonstrated diffuse cerebral edema with cerebellar tonsillar herniation. No aspirin, salicylate, or hepatotoxic exposure was identified. Forensic autopsy revealed severe cerebral edema with tonsillar herniation and an antemortem intracardiac thrombus (2.5 cm) adherent to the tricuspid valve. Histopathology confirmed diffuse hepatic microvesicular steatosis without inflammation, necrosis, or fibrosis, and lines of Zahn within the thrombus. Toxicological and infectious investigations were negative. Because postmortem metabolic screening was unavailable, an inherited metabolic disorder could not be excluded. Death was attributed to brain herniation secondary to severe cerebral edema in a Reye-like clinicopathological syndrome. This case underscores the diagnostic value of integrated forensic investigation in resource-limited settings and highlights the medico-legal importance of distinguishing incidental antemortem intracardiac thrombosis from postmortem clots.