What are the features of Reyes syndrome?

Reye Syndrome Features

Reye syndrome is characterized by acute non-inflammatory encephalopathy with altered level of consciousness, elevation of ammonia levels 24-48 hours after mental status changes, and hepatic dysfunction with fatty metamorphosis or significantly increased liver enzymes, typically following a viral illness with a clear association with aspirin therapy. 1, 2

Clinical Presentation

Primary Features

• Prodromal viral illness (particularly influenza B) followed by:
  • Protracted vomiting (initial symptom)
  • Encephalopathy in afebrile patients
  • Minimal or absent jaundice
  • Hepatomegaly (in 50% of patients) 1

Neurological Manifestations

• Neurological symptoms typically occur 24-48 hours after vomiting onset
• Lethargy is usually the first neurological manifestation
• Progressive neurological deterioration:
  • Altered level of consciousness
  • Confusion
  • Agitated delirium
  • Seizures
  • Coma 1, 3

Additional Features

• Diarrhea and hyperventilation may be first signs in children younger than two years
• Metabolic acidosis is consistently present
• Renal and cardiac dysfunction may occur 4
• Ammonia elevation 24-48 hours after mental status changes (most frequent laboratory abnormality) 1

Laboratory and Diagnostic Findings

Key Laboratory Findings

• Hepatic dysfunction with:
  • Fatty metamorphosis on liver biopsy OR
  • More than threefold increase in ALT/AST 1
• Elevated ammonia levels (hallmark finding)
• Metabolic acidosis 4

Imaging and Other Investigations

• Head CT may reveal cerebral edema but results are often normal
• EEG may show slow wave activity in early stages and flattened waves in advanced stages
• CSF may have increased opening pressure with minimal white blood cells (<9/ml, usually lymphocytes) 1

Atypical Presentations

Some cases present with atypical features:

• Transient hematological changes
• Dissociation between hepatic metabolic impairment and neurological findings
• Severe EEG abnormalities with only mildly altered neurological examination 4

Epidemiology and Risk Factors

• Rare condition, primarily affecting children and adolescents
• Strong association with aspirin use during viral illnesses
• Dramatic decline in incidence following warnings about aspirin use in children
• Children on long-term aspirin treatment for medical conditions may be at increased risk if they develop influenza infection 1, 2
• More prevalent in older adolescents who may self-medicate 5

Prognosis

With earlier diagnosis and more aggressive therapy, mortality has fallen from 50% to less than 20% 1, 2. Prognosis is related to:

• Stage of syndrome at presentation
• Rapidity and adequacy of intensive care treatment 4

Differential Diagnosis

When evaluating a patient with suspected Reye syndrome, consider other conditions that can present with similar features:

• Inborn errors of metabolism (many children with Reye syndrome have underlying metabolic disorders)
• Other causes of acute liver failure
• Encephalitis
• Toxic ingestions 1, 2

Early recognition and prompt management are critical for improving outcomes in patients with Reye syndrome.