Combination of Hyperammonaemia and Tachyarrhythmia in a Newborn with Carnitine-acylcarnitine Translocase Deficiency

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.