"In the Quarter Horse breed as a whole, researchers found the highest incidence of PSSM and GBED, with about 11 percent of individuals testing positive for those genes, but there was a lower incidence of HERDA (3.5 percent) and HYPP (1.5 percent).
However, disease-causing genes were distinctly distributed within the seven subgroups of performance Quarter Horses competing at the highest level of their discipline.
Of the halter subgroup, 56 percent of the individuals carried the genes for HYPP and 28 percent carried the genes for PSSM.
The cutting, reining and working cow horse subgroups all contained the genes causing HERDA, PSSM and GBED. In the cutting subgroup, 28 percent of the individuals carried the gene for HERDA.
In the western pleasure subgroup, genes for GBED had the highest incidence at 26 percent, although HYPP, PSSM and HERDA were also present.
The barrel racing and racing subgroups had the lowest frequencies of the diseases tested for, with only PSSM appearing in the racing subgroup.
LWFS did not appear in any of the groups, although researchers believe it could appear in a larger sample population due to the number of registered Quarter Horse mares that have produced foals with the recessive disease when bred to Paint stallions."
I have often seen people talk about hypp lately, but PSSM and GBED seem to be a much bigger problem in the QH breed. I have found a facebook group about it and there were some names given, but are there lists of PSSM positive horses?