Genetic Test for Equine Immune-Mediated Myositis

Tech ID: 29366 / UC Case 2017-280-0


Researchers at the University of California, Davis and Michigan State University have developed a genetic test to diagnose immune-mediate myositis in American Quarter Horses and related horse breeds.

Full Description

Immune-mediated myositis (IMM) is a disorder in which the immune system attacks skeletal muscles, causing rapid atrophy of the muscle tissue. IMM is predominantly found in American Quarter Horses and is characterized by rapid-onset muscle atrophy often causing wasting of 40% of the mass of the topline muscles in a matter of days. IMM is responsive to treatment with corticosteroids to halt muscle wasting with return of muscle mass over months. Current diagnosis of IMM in horses involves the measurement of serum creatine kinase and aspartate transaminase, with a definitive diagnosis requiring biopsies of the atrophied rump/back muscles.

Researchers at the University of California, Davis and Michigan State University have discovered the genetic mutation for immune-mediate myositis in breeds related to the American Quarter Horse and have created a genetic test for this disease. Horses that are homozygous or heterozygous for the mutation may develop IMM or severe nonexertional rhabdomyolysis. The disease is often triggered by environmental factors such as infection or vaccination in genetically susceptible horses. The mutation is highly associated with the IMM phenotype and can be used with related breeds.This test can be used in breeding stock to minimize the occurrence of IMM.


  • Genetic testing for horse susceptibility to IMM and nonexertional rhabdomyolysis
  • Diagnosis of IMM in Quarter Horses, Paint Horses and related breeds


  • Identified genetic mutation

Patent Status

Country Type Number Dated Case
Patent Cooperation Treaty Published Application 2018218049 11/29/2018 2017-280

Additional Patent Pending


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  • Finno, Carrie J.

Other Information


equine, genome-wide association, IMM, quarter horse, immunology, myopathy, myosin heavy chain 1, immune-mediate myositis, horse breeding, muscle atrophy, nonexertional rhabdomyolysis, genetic mutation

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