How is Reye syndrome primarily defined?

Reye syndrome is primarily defined by the presence of fatty liver accompanied by encephalopathy. This syndrome typically occurs in children and is associated with the administration of aspirin during viral infections, particularly influenza and varicella (chickenpox). In Reye syndrome, the liver becomes swollen and fatty, which can lead to a range of symptoms including vomiting, confusion, seizures, and ultimately, loss of consciousness. The encephalopathy part refers to the dysfunction of the brain, which can lead to serious complications.

The other options, while they may describe symptoms or conditions that occur in different scenarios, do not accurately capture the defining characteristics of Reye syndrome. Severe dehydration with renal failure is not specific to Reye syndrome, as it can occur in various clinical conditions, particularly during illnesses that lead to excessive fluid loss. Extreme fatigue with hypoglycemia is more characteristic of different metabolic disorders. Acute respiratory distress is unrelated and pertains to lung and breathing issues, which do not play a role in the pathophysiology of Reye syndrome. Thus, the defining features of fatty liver and encephalopathy are what distinctly classify this condition.