PSSM.eu

Research has shown that PSSM type 1 is hereditary and dominant. This means that if a horse that carries one or more genes that cause PSSM, iit can pass on these genes to its offspring, causing its offspring to exhibit symptoms of PSSM as well.
The genes that have been discovered that cause symptoms of PSSM type 2 are considered to be semi-dominant, meaning that if a horse inherits the gene from one of its parents (horse carries one copy of the gene), it is affected and likely to develop symptoms whereas a horse that inherits a copy of the gene from each parent (horse carries two copies of the gene) will be more severely affected.