PSSM causes a lot of pain and suffering in horses. Given that it is a hereditary disease, selective breeding can prevent the disease from spreading. It is not certain which bloodlines carry the PSSM gene, although there are some bloodlines in which the PSSM is more prevalent. The PSSM genes are hundreds if not over a thousand years old and consequently have been spread out over many breeds and many bloodlines. For this reason, it is always a good idea to test both broodmares and breeding stallions. The only way to prevent the disease from spreading, is to not breed it forward.


Testing for PSSM type 1 is straight forward and non-intrusive. All you need to do is pull some mane or tail hair with the roots in tact (the roots contain the DNA used for testing) and send it in with a submission form.

Options for testing are for example Generatio/Center for Animal Genetics (CAG) in Germany, Laboklin in Germany and the Dr. Van Haeringen Laboratory in Wageningen, the Netherlands. See  , or  for more information on how to submit your samples.


Until recently, the only way to diagnose PSSM type 2 was by muscle biopsy. This option, which is currently still considered the only scientifically validated medical diagnostic tool for PSSM type 2, requires a specialist to come to the correct diagnosis. Ask your vet about the options. A muscle biopsy provides insight into the state of the muscle tissue at the time the biopsy was done. A biopsy can be negative for PSSM type 2, but this does not necessarily mean the horse does not have PSSM type 2.

EquiSeq, an American based company, has identified several different genes that cause symptoms associated with PSSM type 2. These variants have been named P2, P3, P4, P8, K1 and Px. Their research data are currently being prepared for publication, but the company does offer horse owners the possibility to have their horse tested for these variants. USA based horse owners can send in a hair sample to; horse owners in Europe can send in a hair sample to

Another gene that has been identified as a gene that causes severe muscle wasting is the MYH1 gene, that predisposes a horse to developing Immune Mediated Myositis. This condition is specific to Quarter Horses and related breeds and can be tested at for example Laboklin or Animal Genetics (see links above).