Autism and metabolic diseases.

Autism is an etiologic heterogeneous entity caused by many different diseases occurring in the central nervous system at an early stage in life. Several metabolic defects have been associated with autistic symptoms with a rate higher than that found in the general population. Inborn errors of metabolism can probably account for less than 5% of individuals. Selective metabolic testing should be done in the presence of suggestive clinical findings, including lethargy, cyclic vomiting, early seizures, dysmorphic features, and mental retardation. In some patients, early diagnosis of the metabolic disorders and proper therapeutic interventions may significantly improve the long-term cognitive and behavioral outcome.