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CDC diagnostic criteria
Pathophysiology
Reye syndrome appears to involve mitochondrial injury resulting in inhibition of oxidative phosphorylation and fatty-acid β-oxidation usually in a virus-infected, sensitized host, most commonly with recent upper respiratory tract illness, chickenpox, or diarrheal illness, in association with exposure to mitochondrial toxins, most often salicylates.
Histologic changes include cytoplasmic fatty vacuolization of hepatocytes, astrocyte edema and loss of neurons in the brain, and edema and fatty degeneration of the proximal lobules in the kidneys. Hepatic mitochondrial dysfunction results in hyperammonemia, thought to induce astrocyte edema, which causes cerebral edema and increased intracranial pressure (ICP).
Etiology
Pathogens
Influenza A and B, and varicella-zoster are the pathogens most commonly associated with Reye syndrome. Other pathogens include parainfluenza, adenovirus, coxsackie, herpes, rubella, measles, cytomegalovirus, Epstein–Barr, HIV, retrovirus, hepatis A and B, mycoplasma, chlamydia, pertussis, shigella, salmonella, and poliomyelitis. Reye syndrome can occur after vaccination with live viral vaccines.
Salicylates
Epidemiologic studies have demonstrated association of Reye syndrome with salicylates, particularly aspirin. More than 80% of patients with Reye syndrome had taken aspirin in the past 3 weeks, and recommendations that children not be treated with salicylates led to an immediate and dramatic decrease in the incidence of Reye syndrome.
Other medications
Valproate, warfarin, zidovudine, didanosine, tetracycline, and some neoplastic drugs have been associated with Reye or Reye-like syndrome. Nonsteroidal anti-inflammatory drugs, including sodium diclofenac and mephenamic, are thought to produce or worsen Reye syndrome. Association with acetaminophen and antiemetics was postulated but not substantiated.
Toxins
Insecticides; herbicides; aflatoxins; isopropyl alcohol; paint; paint thinner; margosa (neem) oil; hepatotoxic mushrooms; hypoglycin in ackee fruit (Jamaican vomiting sickness); and herbal medications with atractyloside, a diterpenoid glycoside in extracts of the tuber of Callilepis laureola (impila poisoning), and Bacillus cereus cereulide toxin have been reported to cause Reye syndrome.
IEMs
Reye-like syndrome is caused by fatty-acid oxidation defects, particularly medium-(MCAD) and long-chain acyl dehydrogenase deficiency (LCAD), urea-cycle defects, amino and organic acidopathies, primary carnitine deficiency, and disorders of carbohydrate metabolism.
Epidemiology
In the United States, cases reported to the Centers for Disease Control (CDC) peaked at 555 in 1979–1980. Between 1987 and 1993, a maximum of 36 cases were reported annually, and since 1994, ≤2 cases annually. Although CDC reporting is no longer mandated, reporting is still required by many local/state health boards.
Presentation
Abrupt onset of pernicious vomiting occurs 12 hours to 3 weeks (mean, 3 days) after symptoms of viral illness have resolved. Diarrhea and hyperventilation may be the first signs in children < 2 years old. Neurologic symptoms usually occur 24 to 48 hours after the onset of vomiting, beginning with lethargy and progressing to irritability, agitation, delirium, seizures, and coma.
Exam findings may include dehydration, hepatomegaly, lethargy, encephalopathy, obtundation, coma, seizures, and paralysis. Notably patients are afebrile with minimal or absent jaundice.
Findings may also include acute respiratory failure, aspiration pneumonia, cardiac arrhythmia, myocardial infarction, cardiovascular collapse, gastrointestinal bleeding, and pancreatitis.
Clinical staging
Lovejoy described five clinical stages of Reye syndrome 1–5. Hurwitz added a nonclinical stage (i.e., stage 0). The CDC added stage 6 for patients who cannot be classified due to treatment. Stage 0 does not meet the CDC case definition, because it does not meet the clinical criteria (Table 80.2).
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