Seeing double: the low carb diet

A 38 year old white Scottish man with mild learning difficulties (able to read and write but not to maintain employment) presented with a three day history of diplopia and agitation, after seven days of presumed viral gastroenteritis.

On admission, he was agitated, mildly confused, tachycardic (115 beats/min, regular) and tachypnoeic (18 breaths/min). There were no chest signs or peripheral oedema. He had complete bilateral sixth cranial nerve palsies and horizontal nystagmus, with dilated, slowly reacting pupils. Limb movements were clumsy, with moderate cerebellar signs and dysdiadochokinesis, but no tremor. He was clinically jaundiced. Electrocardiography showed inferolateral T wave inversion. His heart size was at the upper limit of normal on chest radiography.

On specific questioning, he gave a history of lifelong avoidance of alcohol, but of 34 kg weight loss over the preceding three months. This information was corroborated by his parents and practice nurse. At an initial weight of 127 kg (body mass index 42.4), he had received “healthy eating” advice from his practice nurse, who described him as her “star patient.” His weight had rapidly fallen—from 123 kg at four weeks, to 110 kg at eight weeks, 104 kg at 11 weeks, and finally 93 kg (body mass index 31) on admission. More recently, pursuing greater weight loss, he had eliminated all bread, cereals, and fats, on a diet considered “starvation” by his parents, without nutritional supplements.