HYPP Presented by the lovely Margaret Dixon

What is HYPP? Also known as Hyperkalemic Periodic Paralysis and Impressive’s Syndrome, this is a disease of the muscular system It is caused when a genetic mutation disturbs the protein called a sodium ion channel which is a “door” in the muscle cells. When this occurs, the SIC’s normal opening and closing is interrupted, allowing sodium levels to rise rapidly. In turn, that changes the muscle voltage of the cells which causes weakness or twitching (Spier). Interestingly, high levels of potassium are usually present in the blood stream when such an attack occurs.

Its Origins The genetic history of this devastating disease is clearly traced back to a famous stallion named Impressive. Impressive He won everything he showed in and people of all calibers and disciplines wanted to breed their mares to him. Several years later people noticed some of their halter babies were having unexplained muscular weakness and paralysis. The reason was discovered after researchers figured out all of them had a common ancestor: Impressive (Spier).

Origins continued It was discovered that Impressive, despite never showing any symptoms, had a genetic mutation that was passed down to his offspring along with his good looks and wonderful personality. Of the 14 big name halter studs that stood after Impressive was retired, 13 of them were by Impressive and all were either positive for HYPP or carried the genetic trait for it.

It can happen to a variety of horses. Note through that they are all stocky muscular horses and all have Impressive in their pedigrees.

What are the symptoms? Symptoms range from mild muscular twitching that is unnoticeable to the naked eye, visible twitching, crawling of the skin, hindquarter paralysis and in extreme cases, paralysis of the heart and lung muscles (Life)

What does it look like? This is a video clip of a broodmare who is suffering an attack.

This is another video clip showing a mare with muscular twitching and “crawling” skin

What does HYPP affect? It is commonly found in horses with extremely muscular horses, especially these with a pedigree that traces back to Impressive. Not all horses that have Impressive blood in them do have HYPP, a fact that is much endorsed by their owner if they are attempting to sell that horse or stand it for stud. It is also found in some other stock type horses such as appaloosas and paints, again with lineage that traces back to Impressive. HYPP is also found in humans, but it is not as common to have it as, say, having your leg bitten off by a great white.

What does it have to do with us? Because this can be potentially deadly to the horse that test positive for it, it is important that we continue to empathize not breeding to the next “hot” stallion, but to breed for a genetically diverse pool that will produce vigorous and healthy horses (Life). HYPP can also affect humans- if we can find a cure for the horses afflicted with HYPP, it is possible we can find a cure for people who suffer from this disease.

Why? I chose this because one of my horses is HYPP positive and the other one, while negative for it, carries the gene. My horse who is HYPP positive has never had an episode but we maintain him on medicine and he has a very strict diet. It is a hard thing to have to deal with and I will NEVER have another horse that is positive for it.

My baby, Six- he is positive for HYPP

References Spier, Sharon J. Veterinary Genetics Laboratory. 7 Apr.-May UCDavis. 10 Sept Spier, Sharon J. Veterinary Genetics Laboratory. 7 Apr.-May UCDavis. 10 Sept