Background

RS is a biphasic illness. A viral prodrome—with infection of the upper respiratory tract or bowel, or varicella—is followed several days later by an abrupt onset of encephalopathy heralded as profuse, effortless vomiting. The rate and degree of neurological decline vary. Raised intracranial pressure from brain swelling is usually thought to cause death or neurological injury.

The British Paediatric Surveillance Unit defines RS as an unexplained, non-inflammatory encephalopathy in those less than 16 year of age, associated with a serum aspartate or alanine aminotransferases, or plasma ammonia more than three times the normal limit, or hepatic fatty infiltration that is microvesicular in appearance and panlobular in distribution.2 Diagnostic criteria are non-specific. One group maintains that antiemetics taken after onset of the vomiting have a causal role in RS, another disputes its actual existence3 ,4; evidence in support of these views is unconvincing and they have gained little support. However, a proportion of those thought initially to have RS (12%) are shown later to have an inherited metabolic disorder (IMD), such as single enzyme defects of β oxidation, or the urea cycle.2 “Classical” RS must of necessity be a diagnosis of exclusion.

Aspirin—a co-factor?

The evidence on prodromal aspirin and RS has been reviewed.5 Several case–control studies assert that the association is strong, consistent, and …