11/23/2024
IMM/MYH1
Immune-mediated myositis (IMM) is a muscle disorder in horses that's caused by a mutation in the myosin heavy chain 1 (MYH1) gene. IMM is one of two clinical presentations of Myosin Heavy Chain Myopathy (MYHM), an autoimmune disease that affects a horse's muscle cells:
Immune-mediated myositis (IMM)
An autoimmune disease that causes rapid muscle loss and stiffness. The immune system attacks the horse's own muscle fibers, resulting in muscle atrophy in the back and rump.
Nonexertional rhabdomyolysis
Also known as "tying up", this condition causes severe muscle damage without muscle atrophy. Symptoms include dark urine, high muscle enzyme levels in the blood, and hard, stiff muscles.
IMM is most common in Quarter Horses and related breeds, but it can affect any horse. Symptoms usually appear before age 8 or after age 17.
IMM can't be cured, but it can be managed.
Immune-Mediated Myositis and nonexertional rhabdomyolysis.
UC Davis Center for Equine Health
Myosin Heavy Chain Myopathy (MYHM) in Horses:
Feb 17, 2023 — IMM describes episodes of severe muscle atrophy in horses with the MYH1 genetic mutation. IMM involves an immune system attack (autoimmune response)
Mad Barn
MYH1 Myopathy is an autoimmune disease where a horse can have an immune reaction against its own muscle cells.
Tri-State Livestock News
Immune Mediated Myopathy (IMM) - Animal Genetics
Although IMM itself cannot be cured, this disorder can be managed. Corticosteroids are primarily used to help a horse ease off of an autoimmune episode. Mar 28, 2024 — Immune-mediated myositis (IMM) is a muscle disorder in horses where the immune system mistakenly attacks its own muscle fibers
UC Davis
https://vgl.ucdavis.edu › ...
Myosin-Heavy Chain Myopathy (MYHM)
by F Avila — Myosin-heavy chain myopathy (MYHM) is a muscle disease in Quarter Horses and related breeds that results in two distinct clinical disease presentations.
UC Davis Center for Equine Health
https://ceh.vetmed.ucdavis.edu › ...
Immune-Mediated Myositis / Nonexertional Rhabdomyolysis
Aug 5, 2019 — MYHM describes two muscle diseases caused by a mutation in the MYH1 gene; immune mediated myositis and nonexertional rhabdomyolysis.