Sudden child death and 'healthy' affected family members with medium-chain acyl-coenzyme A dehydrogenase deficiency.

A family is described in which the father and three (and probably all four) of his children had a decreased capacity for the oxidation of medium-chain fatty acids. One of the children suddenly died at the age of 16 months following an episode of a rapidly deteriorating Reye syndrome-like illness with hypoketotic hypoglycemia and dicarboxylic aciduria, but without any previous alarming symptoms. The eldest sibling had died at the age of 19 months under similar conditions. The other family members had always been healthy. On fasting, all affected family members accumulated in their plasma the medium-chain fatty acids octanoic, decanoic, and cis-4-decenoic acids. Their urinary organic acid excretion profile could be characterized as "dicarboxylic aciduria." A deficiency of medium-chain acyl-coenzyme A dehydrogenase was demonstrated in a postmortem liver sample of the index patient. Cultured fibroblasts from the father and the two healthy children had a decreased rate of [14C]octanoate oxidation. It is suggested that a deficiency of medium-chain acyl-coenzyme A dehydrogenase may lead to a life-threatening illness when other complicating factors such as diarrhea and vomiting result in an abnormal depletion of the body's glycogen stores. Careful monitoring of at-risk patients during a minor illness is necessary.