Originally Posted by Arksly
I have never even heard of HYPP... What is it and what do horses look like when they have it?
HYPP is also known as "Impressive Syndrome". It is a genetic defect that traces soley back to Impressive, who was, as his names says, an impressive horse. He is the sire that basically defined the look of todays quarter horse. People were so drawn by his look that they bred to him very heavily. It wasn't until many years later that HYPP was actually given a name and then it took quite some time before it was traced back to Impressive. So they disease spread for many years with the public having little knowledge about it.
AQHA has since implemented rules stating that foals that are not HYPP/NN can not be registered. (HYPP is an inherited desease that comes only from descendents of Impressive - and in order for them to pass it on, they must carry the gene.)
HYPP stands for hyperkalemic periodic paralysis. This condition is characterized by intermittent episodes of muscle tremors (shaking or trembling, weaknesses and/or collapse.)