Reye-like syndromes

Many rare genetic (inherited) disorders of the body chemistry - called metabolic disorders - are known to cause a disorder similar to Reye's syndrome. We provide information on what is known about these syndromes and why they are important. We also give a note on screening in newborn babies.


Many rare, genetic (inherited) disorders of the body chemistry (metabolic disorders) are now known to cause a disorder similar to Reye’s syndrome. The early treatment of these Reye-like disorders is similar to that of Reye’s syndrome. But some require special drugs or diets for treatment and to prevent recurrence of the disorder.

Special laboratory tests are required to make certain that such disorders are excluded in all children and young persons with suspected Reye’s syndrome.

Other children and young persons in the family may also have the genetic disorder in a latent form.

These disorders may also rarely manifest for the first time in teenagers and in older adults.

What are Reye-like syndromes?

“Reye’s Syndrome” is the name given to what is now believed to be not one, but a number of childhood disorders. These disorders 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’s 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 identified 26 inherited disorders of body chemistry also called inherited metabolic disorders (IMD’s) or inborn errors of metabolism (IEM’s) which can very readily be confused with classic Reye’s syndrome. These 26 Reye-like disorders are listed in the Metabolic Disorder section may meet the diagnostic criteria but should nowadays be specifically sought for and excluded, before true Reye-syndrome is accepted as the final diagnosis.

In the UK this careful approach has meant that 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 fatty acid oxidation (lipid metabolism), amino acid metabolism, carbohydrate metabolism and disorders of ammonia detoxification (other defects).

Similar illnesses that may resemble Reye’s syndrome during early stages

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, eg 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 they 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.

Newborn screening

In the UK every baby is offered newborn blood spot screening, also known as the heel prick test, ideally when they are five days old.

The blood spot tests screen for nine rare but serious conditions, six of these disorders are inherited metabolic diseases, three of which are “Reye-like” viz

  • medium-chain acyl-CoA dehydrogenase deficiency (MCADD)
  • maple syrup urine disease (MSUD)
  • isovaleric acidaemia (IVA).

Date of next review: January 2022