Introduction Leigh Syndrome is a rare progressive neurometabolic disorder. Perinatal onset has been previously reported. Very few of these infants have been reported to be encephalopathic at birth. Differentiation between hypoxic ischaemic encephalopathy and perinatal Leigh disease can be difficult as the clinical presentation and radiological findings can be similar.

Case Report A male infant was delivered at 38⁺⁶ weeks, weighing 3060g by emergency caesarean section due to persistent fetal tachycardia with reduced variability. He was the first child of healthy non-consanguineous parents. He was mechanically ventilated at birth due to lack of spontaneous breathing but did not need any other resuscitation. He was severely encephalopathic since birth and received therapeutically hypothermia for 72 h. He had severe lactic acidosis which responded to Na-dichloroacetate. Cerebral function monitoring showed burst suppression pattern with severely suppressed trace and showed no recovery following hypothermia. Electroencephalogram showed extremely low amplitude suggestive of severe cortical dysfunction. MRI brain on day 8 revealed bilateral symmetrical focal signal changes involving the basal ganglion, internal capsule, brainstem and perirolandic region; features favouring profound hypoxic-ischaemic insult. He continued to remain severely encephalopathic disproportionate to the hypoxia sustained at birth, raising the suspicion of a metabolic condition. All metabolic investigations and muscle respiratory chain enzymes were normal. Muscle biopsy showed immature muscle with scattered fibres containing increased lipid. MTO1 and RMND1 genetic analysis was normal. Due to lack of clinical improvement, intensive care was discontinued on day 11 leading to his demise. The post-mortem neuro-histology showed chronic grey and white matter damage with neuronal calcification, microglial response, glial scars, capillary response, cyst formation and most importantly, relative neuronal preservation in necrotic foci (the latter not usually seen in hypoxic encephalopathy) confirming Leigh disease.

Conclusion Encephalopathy at birth in absence of clear history of perinatal hypoxia should prompt consideration of wider differential diagnosis of possible neuro-metabolic cause. The differentiation is important for subsequent management, prognostication, and future genetic counselling and also for medicolegal purposes questioning the adequacy of perinatal management. It also emphasises the value of post-mortem in such cases to clinch the diagnosis.