Endocrine Abstracts

A 42-year-old female had extensive neurological investigations (normal MRI brain, EEG, NCS). A low CSF glucose triggered endocrine referral. She had a history of ill health/fatigue since 19 years when she had a viral illness with seizure-like episode and transient wheelchair dependance, with no formal diagnosis made. She had recurrent symptoms including fatigue, myalgia and weakness, with some relation to hunger and fasting.

Physical examination revealed macrocephaly, mild generalised reduction in power and ataxia, with brisk bilateral lower limb reflexes.

A full fatigue screen was normal. Prolonged fasting led to symptoms at 24 h of fatigue, left calf pain and multiple episodes of rhythmic left leg jerking lasting approximately 20 s, during which she was fully conscious. Clinical examination demonstrated left hemiparesis (4/5) and reduced sensation. Lab glucose was 4.3 mmol/l, plasma lactate 0.9 mmol/l (0.5–2.2) during the episode. She declined further fasting.

She was referred to the regional adult inherited metabolic disorders team. The history and examination is characteristic of the paroxysmal late-onset form of glucose transporter type one (GLUT 1) deficiency syndrome. This is usually caused by mutations in the SLC2A1 gene and results in impaired glucose transport into the brain. Patients develop classical features of hypoglycaemia with normal peripheral blood glucose. Some marginal changes may occur in serum lactate (i.e. inappropriately low <1 mmol/l) when symptomatic. Lower limb pain and jerking is characteristic. Ketogenic diet is effective in 60% of cases. This is an autosomal dominant condition and is likely to be under-diagnosed. Cases may appear in endocrine clinics because of hypoglycaemic symptoms and hunger. Symptoms may be assumed to be functional or related to chronic fatigue syndrome.