Introduction: Oligophrenia makes 7.3% of all mental disorders in our country. It is known that almost 4% of all diagnosed cases of oligophrenia developed as a result of an inherited disturbance of amino acid metabolism. In most countries, the frequencies of inherited diseases of amino acid metabolism in the population are determined, and preventive screening programs of newborns are implemented. No study has been conducted so far into the issue of inherited diseases of amino acid metabolism in the Mongolian population. The goal of our survey was to detect inherited disorders of amino acid metabolism in the population at risk. Materials and Methods: The collection of samples and the laboratory analysis were carried out in the following two stages:
1. The screening analysis of 514 individuals diagnosed with mental retardation was performed by paper chromatography;
2. The positivecases detected by the screening were analyzed using high-performance liquid chromatography. Results: The screening testing detected twelve potential disturbances of amino acid metabolism. Out of the twelve positive cases four individuals refused to participate in the confirmatory stage of the survey. Among the remained eight individuals, cases of hypertyrosinemia, hypervalinemia, hyperglycinemia, hyperlysinemia and pyridoxine-dependent epilepsy were detected. Conclusions
1. The fact that cases of inherited disorders of amino acid metabolism were detected among mentally retarded individuals show that the disorder is one of causes of oligophrenia.
2. A screening program of newborns should be implemented for early detection of inherited disorders of amino acid metabolism.
3. A genetic counselling and testing centre could assist in reduction of number of individuals with inherited disorders.