Which laboratory finding is characteristic of Reye's syndrome?

• A. Hyperglycemia
• B. Elevated ammonia level
• C. Proteinuria
• D. Elevated cholesterol

Answer: (B)

Reye's syndrome causes acute brain dysfunction due to liver failure from mitochondrial damage, which impairs the urea cycle. This leads to ammonia building up in the blood, making elevated ammonia a hallmark laboratory finding. The excess ammonia is directly neurotoxic and drives the encephalopathy and cerebral edema seen in this condition. Other options don’t fit the pattern of Reye's syndrome: hyperglycemia isn’t typical (often there can be hypoglycemia due to impaired glucose production), proteinuria isn’t a defining feature, and elevated cholesterol isn’t characteristic of this acute hepatic insult.