HyPP stands for Hyperkalemic Periodic Paralysis. It's a genetic disease in horses that has been traced back to a champion AQHA stud Impressive. Impressive is Ricci's [my horses'] paternal grandfather. Impressive died from HyPP.
I decided to look it up. Episodes of HyPP are basically seizures, from mild to severe, lasting from a matter of seconds to several hours. When horses die from this, it's because it paralyzes the muscles of the heart of lungs, and they have a heart attack, or suffocate. However, an episode can also be a twitch in the muscles that can't be seen by the human eye. HyPP basically makes too much potassium for the horses body to handle, causing the episodes I mentioned earlier. They say it's possible it can be managed in N/H or H/H horses [N/H horses got the gene from one parent, H/H got it from both, and N/N is negative] by getting the hay and grain and pastures tested for potassium levels, saying you want no more than 1%.
Impressive was N/H, and statiscally would pass the gene along to 50% of his offspring. So there was a 50% chance that Ricci's sire had it. The HyPP gene is a dominant one. I managed to look up Ricci's sire and found that he was N/N, so Ricci doesn't have it. I'm going to have her tested though, just to be sure.
However, I was appalled to learn that people are knowingly breeding HyPP positive horses, and even more upset that the registries aren't really doing anything about it. HyPP horses typically make great halter horses because of their build, something to do with the potassium I guess. [My horse was never good in halter.] AQHA ruled that H/H horses cannot be registered, but nothing was said about N/H. And I'm sad to report that the APHA hasn't made any rulings regarding HyPP. [My horse is registered to APHA.]
I guess I just wanted to let everyone know about this. I imagine most people have never even heard of it. But I'm putting this out there for all you horse lovers. I want anyone who's unaware to be aware. While some horses can lead a long productive life without so much as an episode, the chances are just as good that it's life will be short and traumatic. HyPP isn't restricted to just QH's and Paints either, it says Arabians, Appaloosas, Pintos and other stock breeds may be at risk. Any horse that has Impressive in it's bloodlines. Here is the website I got most of my information from, I found it really informative.