Inborn urea cycle disorders are under-recognised metabolic causes of hyperammonemia in adults. A 28-year-old primigravida, seven weeks pregnant, affected by hyperemesis gravidarum developed acute liver injury (ALI) and then acute liver failure (ALF) in less than 48 h. Because the patient developed atypical features, especially mildly elevated aminotransferases contrasting with very high blood ammonia levels (281 μmol/L), concomitant with normal serum creatinine, an inborn error of metabolism was suspected. We performed emergency metabolic analyses, stopped all protein intake and started with intravenous (i.v.) high caloric intake, nitrogen scavenger drugs and haemodialysis. The neurological and hepatic status of the patient quickly improved together with normalisation of her ammonemia levels. High plasma glutamine and urinary orotic acid, alongside low plasma arginine, citrulline and ornithine were suggestive of an ornithine transcarbamylase deficiency, later confirmed by molecular analyses. Foetal sex was female, as determined by foetal DNA analysis in maternal blood, and foetal development was unremarkable throughout the pregnancy. Delivery was induced at 39 weeks with a close monitoring of ammonemia levels and i.v. perfusion of carbohydrates and lipids during labour and immediately post-partum to avoid hypercatabolism. Delivery was uneventful and the patient delivered a healthy female baby. Urea cycle disorders should be contemplated in non-jaundiced patients with ALI or ALF, severe hyperammonemia and normal serum creatinine regardless of serum aminotransferase levels. The prompt recognition of this rare condition and the rapid initiation of adequate metabolic therapy are mandatory to prevent irreversible neurological sequelae and to avoid liver transplantation.

中文翻译：

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峰值高氨血症和非典型急性肝功能衰竭：妊娠剧吐期间尿素循环障碍的爆发

先天性尿素循环障碍是成人高氨血症的公认代谢原因。一名怀孕 7 周的 28 岁初产妇受妊娠剧吐影响，在不到 48 小时内发生急性肝损伤 (ALI)，然后发生急性肝功能衰竭 (ALF)。由于患者出现非典型特征，尤其是转氨酶轻度升高，血氨水平非常高 (281 μmol/L)，同时血清肌酐正常，因此怀疑是先天性代谢缺陷。我们进行了紧急代谢分析，停止了所有蛋白质的摄入，并从静脉 (iv) 高热量摄入、氮清除药物和血液透析开始。患者的神经和肝脏状况迅速改善，血氨水平恢复正常。高血浆谷氨酰胺和尿乳清酸，除了低血浆精氨酸，瓜氨酸和鸟氨酸提示鸟氨酸转氨甲酰酶缺乏症，后来通过分子分析证实。根据母体血液中的胎儿 DNA 分析确定，胎儿性别为女性，并且在整个妊娠期间胎儿发育不显着。在 39 周时诱导分娩，并在分娩期间和产后立即密切监测氨血症水平和碳水化合物和脂质的 iv 灌注，以避免过度分解代谢。分娩很顺利，患者分娩了一个健康的女婴。无论血清转氨酶水平如何，无黄疸的 ALI 或 ALF、严重高氨血症和正常血清肌酐患者都应考虑尿素循环障碍。