Objectives:
It has been suggested that some amino acids are involved in the pathogenesis of autistic disorders. The aim of the study was to evaluate the plasma amino acids profile in young males with autism.

Methods:
Total of 27 autistic boys (aged 2–10 years, the study group) without any metabolic disorders and 13 healthy boys (aged 2–9 years, control group) were included in the study. In all subjects fasting blood plasma free amino acids (both exogenous and endogenous) were quantitatively measured by high performance liquid chromatography with UV-VIS detection.

Results:
The mean plasma concentration values of citrulline, .-aminobutyric acid, isoleucine, leucine, phenylalanine, tryptophan and ornithine were significantly lower in boys with autism as compared to the control group (p < 0.03, p < 0.04, p < 0.02, p < 0.02, p < 0.05, p < 0.02, p < 0.05, respectively). The areas under the Receiver Operating Characteristic curves for these amino acids ranged from 0.637 to 0.726. None of the amino acids measured differentiate autistic children from healthy children. The sum of exogenous amino acids was lower in the study group than in the control group but this difference was not statistically significant.

Conclusions:
Lower levels of exogenous amino acids confirm the possible role of these amino acids in autism. Determination of exogenous amino acids in plasma, however, cannot be used as a diagnostic test but it can still support autistic patients care.