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Leigh syndrome — RACP Paediatrics MCQ

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ModerateGeneticsLeigh syndromeRACP Paediatrics

A 14-month-old presents with progressive developmental regression, feeding difficulties, and episodic metabolic crises precipitated by illness. MRI brain shows bilateral symmetric signal abnormalities in the basal ganglia and brainstem. Blood lactate is elevated. What is the most likely diagnosis?

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Correct answer: D — Leigh syndrome

Leigh syndrome (subacute necrotising encephalomyelopathy) is the most common mitochondrial disorder in children. It presents with developmental regression, brainstem and basal ganglia dysfunction, and characteristic symmetric MRI lesions. It can be caused by mutations in nuclear or mitochondrial DNA affecting oxidative phosphorylation. Elevated blood and CSF lactate support the diagnosis.

Reference: RACP Paediatric Curriculum – Metabolic/Genetics; RCH Melbourne – 2023