Sindrom Reye

01Pathophysiology

Reye's syndrome results from widespread mitochondrial injury, predominantly affecting hepatocytes and neurons. The triggering event is the administration of aspirin (or other salicylates) to a child during or shortly after a viral infection, most classically influenza B, influenza A, or varicella-zoster virus.

The salicylate metabolite is believed to act synergistically with the viral infection to uncouple oxidative phosphorylation and inhibit fatty acid beta-oxidation within mitochondria. When beta-oxidation is halted, free fatty acids accumulate inside hepatocytes, producing the hallmark finding of microvesicular steatosis (small fat droplets filling the cytoplasm without displacing the nucleus). Unlike other causes of acute liver failure, the hepatocyte injury is metabolic rather than inflammatory or necrotic. This is why the liver is swollen and fatty but there is no significant hepatocellular destruction and, critically, bilirubin remains normal because the conjugation machinery is relatively preserved despite the metabolic chaos around it. This is the single most important laboratory discriminator tested on exams.

The same mitochondrial failure occurs in the brain. Without adequate oxidative phosphorylation, neurons cannot maintain energy-dependent ion gradients. Cytotoxic edema develops, and intracranial pressure (ICP) rises. This explains the rapid progression from vomiting to lethargy to coma. The encephalopathy is noninflammatory, meaning the cerebrospinal fluid (CSF) is normal with no pleocytosis, which helps separate this from infectious meningitis or encephalitis.

Hypoglycemia occurs because the liver can no longer perform gluconeogenesis effectively, and glycogen stores in the damaged hepatocytes are depleted. Hyperammonemia develops because the urea cycle, also a mitochondrial-dependent process, fails. The ammonia itself contributes to worsening cerebral edema, creating a vicious cycle.

The coagulopathy (prolonged PT/INR) is a consequence of impaired hepatic synthesis of clotting factors, not from DIC, and does not correct with vitamin K alone, which is another testable point.

02Clinical Staging

Reye's syndrome is staged by the severity of encephalopathy. This classification guides prognosis and management intensity.

The transition from Stage I to Stage II or III can happen over hours. Mortality increases sharply beyond Stage III. Staging is primarily used to determine the aggressiveness of ICP management and the need for intubation or neurosurgical intervention.

03Diagnostic Workup

When a child presents with vomiting and altered mental status following a viral prodrome, the first laboratory clue is a markedly elevated serum ammonia alongside elevated transaminases (AST/ALT). These two findings together in a pediatric patient with a recent viral illness should immediately raise suspicion.

The next critical step is checking serum bilirubin. In virtually every other cause of acute liver failure (viral hepatitis, acetaminophen toxicity, Wilson disease), bilirubin is elevated and the patient is jaundiced. In Reye's syndrome, bilirubin is characteristically normal. This finding is the single most tested discriminator and is almost always present in a vignette for a reason: it steers you toward the diagnosis.

A lumbar puncture may be performed to rule out meningitis or encephalitis. The CSF in Reye's syndrome is normal, with no white blood cells, no organisms on gram stain, and normal glucose and protein. If the CSF shows pleocytosis, the diagnosis shifts toward an infectious etiology.

A CT of the head is obtained to evaluate for cerebral edema and to rule out structural causes. It typically shows diffuse swelling without focal lesions.

Liver biopsy is the most accurate test and reveals microvesicular steatosis with mitochondrial swelling on electron microscopy, but it is rarely performed in clinical practice because the diagnosis is typically made clinically and biochemically. On an exam, if the question asks for the "most accurate" or "confirmatory" test, the answer is liver biopsy.

An important step that is often tested as a "next best step" is to order urine organic acids, serum acylcarnitine profile, and amino acids to rule out inborn errors of metabolism (especially medium-chain acyl-CoA dehydrogenase deficiency, or MCADD, and urea cycle defects). These metabolic disorders can mimic Reye's syndrome almost perfectly, and any child younger than 2 years presenting with this picture must have metabolic screening performed.

04Management & Treatment

There is no targeted antidote or pharmacologic cure for Reye's syndrome. Management is entirely supportive and focuses on two priorities: correcting the metabolic derangements and preventing or controlling cerebral edema.

Hypoglycemia correction is the first and most urgent metabolic intervention. A continuous infusion of D10W (10% dextrose in water) should be initiated immediately and titrated to maintain serum glucose above 60 mg/dL. Failure to correct hypoglycemia worsens the neurologic injury. Blood glucose should be checked every 1 to 2 hours during the acute phase.

Cerebral edema management determines survival. For patients in Stage II or higher, an intracranial pressure monitor should be placed. The target is to keep ICP below 20 mmHg and cerebral perfusion pressure (CPP = MAP minus ICP) above 50 mmHg. First-line osmotic therapy is mannitol at 0.25 to 1 g/kg IV, which can be repeated every 6 to 8 hours while monitoring serum osmolality (hold if osmolality exceeds 320 mOsm/kg). Hypertonic saline (3% NaCl) is an alternative, particularly if the patient is hypotensive, as mannitol can cause diuresis and volume depletion.

Coagulopathy is managed with fresh frozen plasma if there is active bleeding or if an invasive procedure such as ICP monitor placement is planned. Vitamin K (phytonadione, 1 to 10 mg IV depending on age) can be administered but will not fully correct the coagulopathy because the problem is impaired hepatic synthesis, not vitamin K deficiency.

Intubation and mechanical ventilation are indicated for patients with a Glasgow Coma Scale below 8 or those in Stage III or higher. Controlled hyperventilation (target $PaC{O}_{2}PaCO\_2$ of 25 to 30 mmHg) can be used as a temporizing measure to reduce ICP via cerebral vasoconstriction, but should not be sustained long-term due to the risk of ischemia.

Head of bed elevation to 30 degrees, maintenance of normothermia, avoidance of hypotension, and minimizing stimulation are standard neuroprotective measures.

Prevention is the most tested management concept. Since the near-elimination of pediatric aspirin use for viral illnesses, the incidence of Reye's syndrome has dropped dramatically. The guideline is clear: aspirin should not be given to any patient under 18 years of age during a febrile illness, with the exception of certain conditions requiring chronic aspirin therapy (e.g., Kawasaki disease, juvenile idiopathic arthritis, post-cardiac surgery). In these cases, the benefit outweighs the risk, and the family should be counseled about the small residual risk.

05Differential Diagnosis & Distractors

06Traps & High-Yield Pearls

The most common way students get this question wrong is by confusing Reye's syndrome with other causes of pediatric acute liver failure and choosing an answer where the patient is jaundiced. Remember: if bilirubin is elevated or the child is jaundiced, it is not Reye's syndrome. Test writers include a normal bilirubin in the vignette deliberately to guide you, and they include jaundice in the distractor diagnoses to tempt you away.

A second common trap involves the age group and the aspirin exposure. The vignette will almost always mention that a child was given "baby aspirin," "a medication containing salicylate," or "a medication her grandmother recommended for fever" during a recent bout of flu or chickenpox. If you do not recognize the aspirin link, you may default to a diagnosis of viral encephalitis or meningitis, but the normal CSF in the question will argue against that.

A third trap is confusing Reye's syndrome with inborn errors of metabolism, particularly in infants. If the patient is under 2 years old, the question may actually be testing whether you know to order a metabolic workup (urine organic acids, acylcarnitine) before finalizing a Reye's diagnosis. Any recurrence of similar episodes in the history argues strongly for a metabolic disorder, not Reye's.

Finally, students sometimes select "N-acetylcysteine" as the treatment because they see "liver failure in a child" and jump to acetaminophen toxicity. The key difference is that acetaminophen toxicity produces very high transaminases (often in the thousands) and elevated bilirubin, whereas Reye's shows moderately elevated transaminases with normal bilirubin.

The core competency being tested is pattern recognition: a biphasic illness (viral prodrome followed by vomiting and encephalopathy), the aspirin exposure, the paradox of liver failure without jaundice, and knowing that management is entirely supportive with a focus on ICP control and glucose correction.