[Spanish multicenter study: hyperammonemia not associated with inborn errors of metabolism in children]

The hyperammonemic encephalopathy induced by causes different from inborn errors of metabolism is a relatively uncommon but severe complication.

To study the characteristics of a secondary hyperammonemia episode to discern the triggering causes to get to the diagnosis, and the development in the therapeutic intervention.

A multicenter retrospective study of children with hyperammonemia unrelated to inborn errors of metabolism, conducted in Spanish hospitals.

Nineteen patients were selected; hyperammonemia developed in infants under one year old in 47% of them, being diagnosed mostly with two or more symptoms. The most common clinical finding was an altered consciousness level similar to that of intoxication symptoms, followed by seizures. These clinical symptoms were present in 14 patients, with one of them or both. Twelve of the 19 patients were in treatment with more than two antiepileptic drugs routinely. All children were treated with protein restriction (n: 10), scavengers (n: 10) and/or carglumic acid (n: 12) for the treatment of hyperammonemia.

This study suggests that secondary hyperammonemia could be underdiagnosed because it is only detected when severe symptoms appear. Risk seems to be higher in those patients receiving antiepileptic drugs or those critically ill with a restricted diet or incremented metabolism. The response to specific treatment is adequate but should be established earlier to avoid neurological sequelae of this entity.