CASE DESCRIPTION

A 19-year-old female university student presented with a 5-week history of generalised weakness, unsteady gait and breathlessness. There were no symptoms of recent infection. Her only medical history was long-standing symmetrical 40 dB sensorineural hearing loss. On neurological examination, she had hyperpnoea, mild non-fatigable global weakness, bilateral ptosis, soft speech and absent lower limb reflexes.

The MR scan of brain showed symmetric T2-hyperintensities surrounding the third ventricle, hypothalamus and brainstem on fluid-attenuated inversion recovery sequences, suggestive of Leigh syndrome (figure 1). Lumbar puncture showed an opening pressure of 8 cm water. Cerebrospinal fluid (CSF) was acellular, protein 0.38 g/L (normal <0.45) and glucose 3.5 mmol/L (normal 2.2–4.5). Serum lactate and pyruvate were both elevated: lactate 4.3 mmol/L (normal 1.2–2.8) and pyruvate 0.26 mmol/L (normal <0.1).¹ Arterial blood gases …