Viral infections reye s syndrome

REYE'S SYNDROME

This rare encephalopathy, associated with fatty changes in the liver and other viscera, is almost exclusively confined to children. It is due to aspirin useage in infection with Influenza A, Influenza B or varicella-zoster viruses. Incidence

< 1 per 100 000 children per year. Commoner in rural communities. Since 1980 the incidence of this condition has dropped dramatically. Pathology

Neurons and glial cells are swollen; the liver, heart and kidney show fatty infiltration. Pathogenesis

Viral synergism with an environmental factor, e.g. salicylates, may be responsible. Morphological changes in mitochondria indicate a central role.

VIRUS -

+ salicylates + genetic disposition (enzyme deficiency)

Clinical features

Prodromal symptoms of 'viral' infection

BRAIN-

Mitochondrial damage

BRAIN OEDEMA

Brain shift latent period variable duration

Hypoglycaemia

Fails to detoxify substances which disturb neurotransmission

- rapid onset

- vomiting

- delirium

- convulsions

BRAIN DAMAGE

Death results from raised intracranial pressure.

hepatomegaly in 50% focal neurological signs usually absent

- Increase in serum fatty acids

- Aminoaciduria

Investigations

- Raised liver enzymes (ALT & AST) - Hypoglycaemia (in infants)

- Elevated serum ammonia - Prolonged prothrombin time CT/MRI show appearances of diffuse cerebral oedema

Differential diagnosis

Consider other causes of raised intracranial pressure in childhood, especially

- lead encephalopathy,

- lateral sinus thrombosis, e.g. following mastoiditis. Treatment

Treatment aims at lowering intracranial pressure with the aid of intracranial pressure monitoring (see page 50). In addition, blood glucose must be maintained and any associated coagulopathy treated. Reduction of ammonia may be achieved by peritoneal dialysis or exchange transfusion. Prognosis

Early diagnosis and supportive treatment has reduced the mortality from 80% to 30%.

When raised intracranial pressure is present, mortality increases to 50% and a high proportion of survivors have cognitive disorders.

A condition similar to Reye's syndrome occurs in some children with family history of 'sudden infant death'. A deficiency of medium chain acetyl-CoA dehydrogenase (an enzyme essential for fatty acid metabolism) is found. Carnitine deficiency results as a consequence of 'alternative pathway' fatty acid metabolism. Siblings of children with Reye's syndrome should be screened for this disorder.

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