Research on PSSM 2 and MFM Commercial Tests vs. Histopathological Diagnosis in Horses

Research showed a lack of significant association between some commercial genetic tests vs histopathological diagnosis of PSSM2 and MFM.

Equine polysaccharide storage myopathy (PSSM) is one specific form of exertional rhabdomyolysis (ER) that was originally identified in Quarter Horses and related breeds. iStock/Eyecrave

The Equine Veterinary Journal recently published an open-access article titled “Commercial genetic testing for type 2 polysaccharide storage myopathy and myofibrillar myopathy does not correspond to a histopathological diagnosis.” The article was authored by Stephanie J. Valberg, Marisa L. Henry, Melissa Schott and Deborah Velez‐Irizarry of Michigan State University; Carrie J. Finno and Sichong Peng of UC Davis; Erica C. McKenzie of Oregon State University; and Jessica L. Petersen of University of Nebraska-Lincoln.


“Because of the lack of significant association between a histopathological diagnosis of PSSM2 or MFM and the commercial genetic test variants P2, P3 and P4 in WB and AR, we cannot recommend the use of these variant genotypes for selection and breeding, pre-purchase examination or diagnosis of a myopathy.”

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