Which laboratory finding is commonly elevated in Reye's syndrome?

• A. Elevated ammonia level
• B. Elevated AST
• C. Elevated bilirubin
• D. Hyperglycemia

Answer: (A)

Reye's syndrome causes acute brain swelling due to hepatic mitochondrial injury after aspirin use in a viral illness. The liver’s ability to detoxify ammonia by converting it to urea is impaired, so ammonia accumulates in the blood (hyperammonemia). This rise in ammonia is a key lab finding and directly contributes to the encephalopathy and cerebral edema seen in the condition. While liver enzymes like AST can be elevated from hepatocellular injury, and bilirubin may rise later or modestly, the hallmark early finding is elevated ammonia. Hypoglycemia rather than hyperglycemia can occur due to liver dysfunction, and bilirubin elevation is not as prominent early on.