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"Reye's Syndrome" is the name given to what is now believed to be not one, but a number, of childhood illnesses. These illnesses all produce similar symptoms, signs and results of laboratory tests, but they all have different causes. It is thought that so-called "classic" or "North-American-type" Reye's syndrome is an individual disorder in its own right. Its precise cause is not known but there is probably some inherent susceptibility which is precipitated in some circumstances when aspirin is given for a viral infection such as influenza. Unfortunately there is no single laboratory test for "classic" Reye syndrome. Patients are (or should only be) given this diagnosis when all the other causes, the so-called "Reye-like syndromes" have been excluded. The most important "other cause" is one of the over 26 inherited disorders of body chemistry also called inherited metabolic disorders (IMDs) or inborn errors of metabolism (IEMs) which can very readily be confused with classic Reye's syndrome. These may meet the diagnostic criteria but should nowadays be specifically sought for and excluded before true Reye's syndrome is accepted as the final diagnosis. In the UK this careful approach has meant that in just over 10% of reported cases an initial diagnosis of Reye's syndrome has later been revised to an IMD. IM Disorders which may mimic Reye's syndrome include defects in fat oxidation, amino acid metabolism, carbohydrate metabolism and disorders of ammonia detoxification.
There are also a number of other illnesses which superficially may resemble Reye's syndrome in their early stages. These include septicaemia, meningitis, encephalitis, haemorrhagic shock encephalopathy syndrome and acute liver failure without jaundice.
- With wider awareness of the Reye-like disorders, some pointers for them have become clear. Features which may suggest a metabolic disorder rather than Reye's syndrome are:-
the patient is a child under 3 years old.
- a previous history of illness, e.g. vomiting, failure to thrive, encephalopathic episodes, etc.
- a family history of Sudden Infant Death Syndrome or unexpected and unexplained death in sibs.
- absence of vomiting and agitation in the early stages.
- previous history of a similar illness.
Why are the Reye-like illnesses important? Firstly, if they are inherited metabolic disorders then illness is likely to occur at some stage but with treatment may be prevented from doing so. (True Reye's syndrome almost never recurs). Secondly, because these conditions are inherited they may occur in other children in the family. Once again, early recognition and treatment may prevent these children from coming to harm.
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