Endocrine Abstracts

A 24-year-old traffic warden was initially referred to the neurology department with episodes of “funny turns” over the past 7 years. Without warning she would become dizzy and lightheaded with blurring of vision and weak legs. These symptoms would resolve after ingesting something sweet but the relief of her symptoms was not immediate. The episodes could happen at any time of the day but never first thing in the morning and could happen several times a week. She reported that sometimes she gets spasms in her neck and arms, flopping of her head as well as weakness of her legs. She had gained 10 kg over the past year. There was a family history of multiple sclerosis. A MRI of her spine was normal. The neurologist felt that her symptoms were due to hypoglycaemia and she was referred for further investigations. Fasting blood sugars were normal and blood sugars during an attack were also normal. Urea and electrolytes, thyroid function test and creatine kinase were normal. On a subsequent clinic visit she was accompanied by her father who mentioned that the patient’s mother was investigated for similar symptoms when she was 20 years old and several members of her family were also affected with similar symptoms. It transpired that her mother was diagnosed with hyperkalaemic periodic paralysis (PP). The patient was referred to a geneticist. The result of her genetic testing is awaited.

Hyperkalaemic PP is a rare disorder, with an estimated prevalence of 1:200,000. It follows autosomal dominant inheritance with nearly complete penetrance. The cause of hyperkalaemic PP is a change in a gene that regulates the production of a protein (SCN4A) in the sodium channel of skeletal muscle. Dietary modifications to prevent attacks include avoiding foods rich in potassium and avoiding carbohydrate loading.