Introducing Zebras: Impressive Syndrome

David Bertoni

When you hear hoofbeats, think of horses, not zebras. Unless of course you are in Africa, in which case think of zebras and not the rare but majestic Namib Desert Horse...

The zebra segment introduces the weird and unheard of, the MONA of posts...it's edutainment

I thought I'd kick this thing off with a disease uncommon to both horses and humans, Hyperkalaemic Periodic Paralysis.

It's also called Impressive Syndrome because in quarter horses (whatever that is), it can be traced back to a single stallion ancestor named Impressive. Not so in Humans, where it is also known as Gamstorp Episodic Adynamy. Basically, it's an autosomal dominant channelopathy where in the presence of high potassium levels, myocyte sodium channels fail to inactivate and people develop episodic shaking and extreme weakness. Horses have similar symptoms, but also a tendency to sit down and an abnormal whinny. These attacks can be precipitated by ingestion of potassium and potassium rich foods, but also other things like starting exercise, stopping exercise, weather changes, stress, cold weather and fasting. Treatment includes calcium, glucose and diuretics including acetazolamide. And maybe a bag of oats and a rubdown. Potassium levels are normal or occasionally elevated (due to the knock on effects of sodium influx into muscles).  

So next time someone complains of general weakness or collapses and starts shaking, forget checking obs and start taking a family history instead, because you know what it will be. Unless of course, the potassium level is low, in which case it will be the counterpart condition, Hypokalaemic Periodic Paralysis. Seriously.