Abstract: Urea cycle disorders are rare inherited metabolic diseases caused by the decrease or loss of the activity of the enzymes or transporter in the urea cycle，resulting in hyperammonemia，encephalopathy and hepatopathy. Those diseases are preventable and treatable. The disease severity and onset age of the patients with urea cycle disorders depend on the residual enzyme activity，transporter function and the triggers. Most of the patients have the onset in childhood，and hyperammonemia usually appears in the neonatal period or infant period，resulting in severe brain damage or death. It was reported that more than 10% of the patients with urea cycle disorders had the onset after the age of 16 years. Varied neuropsychiatric manifestations were common initial or main symptoms in the late onset patients with partial urea cycle enzyme deficiencies. As reported，the mortality of late onset patients with urea cycle disorders was 11%. Early identification，early diagnosis and early treatment are keys to improving the outcome of the patients.

Key words: urea cycle disorders, late onset, nervous system, hyperammonemia, psychiatric abnormality

摘要： 尿素循环障碍是一组罕见病，为可治可防的遗传代谢病，由于尿素循环中酶或转运体活性减退或丧失导致尿素循环障碍，引起高氨血症、脑病及肝病。尿素循环障碍患者的发病年龄和严重程度取决于残余酶活性或转运体功能及发病诱因，多在儿童期发病，常于新生儿期或婴幼儿期出现高氨血症，导致严重脑损伤甚至死亡。据报道，高达10% 的患儿16岁以后发病，由于部分酶缺陷引起迟发型尿素循环障碍，临床表型复杂。轻重程度不同的神经精神疾病为首发或主要表现。既往报道迟发型尿素循环障碍患者病死率为 11%，早发现、早诊断、早治疗是改善患者预后的关键。

关键词: 尿素循环障碍, 迟发型, 神经系统, 高氨血症, 精神异常