遗传性代谢病引起智力低下的病种较多。这些疾病绝大多数由于酶缺陷造成。酶缺陷导致代谢物降解阻滞,大量在体液、组织（包括中枢神经系统）或脏器内贮积;通过异常代谢途径产生异常代谢产物;产生在正常状态下仅生成微量或根本不出的代谢产物;缺乏具有与智力发育有关的生理功能的物质生成。上述种种异常代谢产物（包括酶所作用的基质的高浓度）可以直接或间接影响脑发育。 一、遗传性氨基酸代谢病 Hereditary metabolic disease caused by mental retardation more. The vast majority of these diseases due to enzyme defects. Enzymatic defects lead to degradation of metabolites block, a large number of storage in body fluids, tissues (including the central nervous system) or organs; abnormal metabolic pathway through the production of abnormal metabolites; produce under normal conditions only produce little or no metabolism Product; Lack of substance with physiological function related to mental development. The above abnormal metabolites, including the high concentrations of substrates on which the enzymes act, can directly or indirectly affect brain development. First, hereditary amino acid metabolism