Amino acids and infantile autism

A metabolic dysfunction may be present in a subgroup of autistic patients. We evaluated a possible impairment of amino acid (AA) metabolism. Thirty-seven autistic patients, with as yet unknown etiology, underwent AA investigation. They were divided into two groups on the basis of clear neurological signs (with and without EEG abnormalities). The two groups were compared with each other and with a third group of 19 normal controls. A primary aminoacidopathy was excluded and no significant AA differences were found between the first and second group of autistic patients. The comparison with controls revealed a higher value of serum tyrosine in the first group and a lower value of urinary cystine in the second group. The hypothesis that the increased tyrosine levels may be linked to dopaminergic dysfunction and the decrease in cystine to opioid peptide alterations is discussed.