[Autism, epilepsy and mitochondrial disease: points of contact]

Abstract

Introduction: Autism is a neurodevelopmental disorder with unknown etiology, although several different specific organic conditions have been found to be associated with autism in about 10 to 37% of cases. Autism with regression has been reported in one third of autistic children with previously normal development. Epilepsy is quite common in autism spectrum disorders. The rate of comorbidity varies between 20-30% of cases, depending upon the age and type of disorder. Major risk factors for epilepsy in autistic children are mental retardation and additional neurological disorders, as well as some specific associated medical conditions like chromosomal abnormalities, phakomatosis and inherited metabolic disorders.

Aim: To review the possible linkage between autism, epilepsy and mitochondrial dysfunction.

Development: The hypothesis of a disturbed bioenergetic metabolism underlying autism has been suggested by the detection of high lactate levels in some patients. Although the mechanism of hyperlactacidemia remains unknown, a likely possibility involves mitochondrial oxidative phosphorylation dysfunction in neuronal cells. Reduced levels of respiratory mitochondrial enzymes, ultraestructural mitochondrial abnormalities and a broad range of mitochondrial DNA mutations suggest a linkage between autism, epilepsy and mitochondrial disorders.

Conclusions: Though mitochondrial disorders are a rare cause of autism in children, we must keep in mind this etiology in autistic patients with epilepsy and associated signs of neurologic and/or systemic dysfunction. Finding biochemical or structural mitochondrial abnormalities in an autistic child does not necessarily imply a primary mitochondrial disorder but can also be secondary to technical inaccuracies or another genetic disorder.