Reye syndrome is a rapidly worsening brain disease. Symptoms of Reye syndrome may include vomiting, personality changes, confusion, seizures, and loss of consciousness. While liver toxicity typically occurs in the syndrome, jaundice usually does not. Death occurs in 20–40% of those affected with Reye syndrome, and about a third of those who survive are left with a significant degree of brain damage.The cause of Reye syndrome is unknown. It usually begins shortly after recovery from a viral infection, such as influenza or chickenpox. About 90% of cases in children are associated with aspirin (salicylate) use. Inborn errors of metabolism are also a risk factor. The syndrome is associated with changes on blood tests such as a high blood ammonia level, low blood sugar level, and prolonged prothrombin time. Often, the liver is enlarged in the syndrome.Prevention is typically by avoiding the use of aspirin in children. When aspirin was withdrawn for use in children in the US and UK in the 1980s, a decrease of more than 90% in rates of Reye syndrome was seen. Early diagnosis of the syndrome improves outcomes. Treatment is supportive; mannitol may be used to help with the brain swelling.The first detailed description of Reye syndrome was in 1963 by Australian pathologist Douglas Reye. The syndrome most commonly affects children. It affects fewer than one in a million children a year. The general recommendation to use aspirin in children was withdrawn because of Reye syndrome, with use only recommended in Kawasaki disease.
For the period 1991–1994, the annual rate of hospitalizations due to Reye syndrome in the United States was estimated to be between 0.2 and 1.1 per million population less than 18 years of age.During the 1980s, a case-control study carried out in the United Kingdom also demonstrated an association between Reye syndrome and aspirin exposure. In June 1986, the United Kingdom Committee on Safety of Medicines issued warnings against the use of aspirin in children under 12 years of age and warning labels on aspirin-containing medications were introduced. United Kingdom surveillance for Reye syndrome documented a decline in the incidence of the illness after 1986. The reported incidence rate of Reye syndrome decreased from a high of 0.63 per 100,000 population less than 12 years of age in 1983–1984 to 0.11 in 1990–1991.From November 1995 to November 1996 in France, a national survey of pediatric departments for children under 15 years of age with unexplained encephalopathy and a threefold (or greater) increase in serum aminotransferase and/or ammonia led to the identification of nine definite cases of Reye syndrome (0.79 cases per million children). Eight of the nine children with Reye syndrome were found to have been exposed to aspirin. In part because of this survey result, the French Medicines Agency reinforced the international attention to the relationship between aspirin and Reye syndrome by issuing its own public and professional warnings about this relationship.