J Hui, KF To, NLS Tang, HC Yau, ELK Law, PC Ng

Abstract

Carnitine-acylcarnitine translocase (CACT) deficiency is one of the fatty acid oxidation defects that presents early in the newborn period. It is known to be associated with a high mortality with a number of the earlier reported cases presenting as sudden infant death syndrome. Like most inborn errors of metabolism, presentation of CACT deficiency is rather non specific. Typical biochemical profile is one of hypoketotic hypoglycaemia with hyperammonaemia. While hyperammonaemia is a common feature for other IEMs like urea cycle disorders and organic acidurias, cardiac arrhythmias especially ventricular tachyarrhythmia are less commonly seen in them compared with fatty acid oxidation defects. Furthermore, patients with CACT deficiency may present without hypoglycaemia. We hereby reported a 5 day old male infant who was diagnosed to have CACT deficiency at post mortem examination. He presented with respiratory distress, deteriorated very rapidly and succumbed within 48 hours of presentation. Though hypoglycaemia was absent at initial presentation, hyperammonaemia and tachyarrhythmias were observed during the course of his rapid deterioration. We believe a combination of neonatal hyperammonaemia together with tachyarrhythymias should raise a strong clinical suspicion towards fatty acid oxidation defects. In Hong Kong CACT deficiency should be considered in this clinical context as it is one of the more commonly seen fatty acid oxidation defects among the Southern Chinese population.

酰基肉碱轉移酶缺乏為脂肪酸氧化缺陷的一種，在新生兒期就會出現早期表現。眾所周知，酰基肉碱轉移酶缺乏有很高的死亡率，在早期報導的嬰兒猝死綜合症中亦佔相當一部份。和大部份的先天性代謝性疾病一樣，酰基肉碱轉移酶缺乏的表現為非特徵性。典型的生化表現為低酮低血糖症或高氨血症。高氨血症為其他先天性代謝性疾病如尿素循環障礙和有機尿酸的常見症狀，而心律失常尤其是室性快速心律失常在先天性代謝性疾病中的發生率較在脂肪酸氧化缺陷中的發生率低。此外，酰基肉碱轉移酶缺乏的病人可無低血糖表現。我們在此報告一例病例，為一個5天大的男嬰在死後被診斷為酰基肉碱轉移酶缺乏。他表現為呼吸窘迫，病情惡化得很快，在發病48小時內死亡。雖然他在初起病時並沒有表現出低血糖，但在病情快速惡化時．出現了高氨血症及快速心律失常。我們相信，同時出現的新生兒高氨血症及快速心律失常令我們高度懷疑脂肪酸氧化缺陷的發生。在此病例中，應該考慮為酰基肉碱轉移酶缺乏，因為在中國華南地區，酰基肉碱轉移酶缺乏在脂肪酸氧化缺陷中的發生率較為普遍。