Early identification of Reye syndrome is crucial. Prompt medical attention can save a child’s life, especially since symptoms may progress rapidly to seizures, coma and death within hours or days. However, most children with Reye syndrome have mild cases that do not worsen.

Reye syndrome usually occurs in a person who has recently contracted a viral illness (e.g., the flu, chickenpox). Signs of Reye syndrome typically appear within a week after onset of the initial infection – at a time when a child appears to be recovering from the original illness.

Symptoms may be mild to severe. When they are mild, the condition may go unnoticed, symptoms do not worsen and the syndrome resolves without treatment, usually within five to 10 days. However, when symptoms are severe, they can progress to death within hours.

Early signs and symptoms of Reye syndrome include:

• Vomiting that is sudden and protracted over many hours
• Lethargy, unusual sleepiness, difficult to awaken
• Disorientation (e.g., confusion, irrational behavior)
• Irritability, aggression, combative behavior
• Hyperventilation
• Liver dysfunction (e.g., swollen, high triglyceride content)

The early signs of Reye syndrome may differ in infants. For example, vomiting may not occur in infants with the syndrome, whereas diarrhea and irregular breathing may appear. 

Additional, more severe signs of Reye syndrome include:

• Delirium
• Weakness in arms/legs, muscle function loss, paralysis
• Unusual posture (arms/legs extended, toes pointed downward)
• Sluggish breathing
• Seizures
• Fixed pupils
• Respiratory arrest
• Coma

The following are NOT symptoms of Reye syndrome:

• Jaundice. Does not usually occur in patients with Reye syndrome. If it occurs, it may indicate a metabolic disorder not associated with Reye syndrome.
  
  
• Fever. Although Reye syndrome does not produce a fever, it may be present in children with the syndrome, since it often accompanies the viral infections (e.g., flu, chickenpox) that precede Reye syndrome.