Rhabdomyolysis

Rhabdomyolysis


image



Basic Information image



Definition


Necrosis of skeletal muscle fibers. Rhabdomyolysis in horses occurs associated with exercise and in nonexercising horses on pasture.



Synonym(s)




• General synonyms: Degenerative myopathy, myonecrosis. Rhabdomyolysis is not inflammatory; therefore the term “myositis” does not apply.


• Exercise-associated rhabdomyolysis: Exertional rhabdomyolysis, tying up, Monday morning disease, myoglobinuria, azoturia, blackwater, setfast, chronic intermittent rhabdomyolysis, recurrent exertional rhabdomyolysis (RER).


• Nonexercising horses: Atypical myoglobinuria, pasture-associated rhabdomyolysis.



Epidemiology



Species, Age, Sex




• Horses, ponies, and mules


• Possible increased risk in females



Genetics and Breed Predisposition


Dominant inheritance confirmed in Thoroughbreds with RER and in horses with polysaccharide storage myopathy



Risk Factors




• The primary risk factor is underlying inherited myopathy. Severe electrolyte disturbance (eg, hypokalemia), selenium deficiency, lack of exercise, anxiety, and high-starch and high-sugar diets increase likelihood of rhabdomyolysis in predisposed horses. Hypokalemia alone may cause rhabdomyolysis, but this is poorly documented.


• Hypothyroidism, vitamin E deficiency, and lactic acidosis are not primary causes of rhabdomyolysis in horses. Severe selenium deficiency may result in severe acute rhabdomyolysis targeting masticatory muscles in adult horses (nutritional myopathy) but does not cause RER.



Associated Conditions and Disorders


Polysaccharide storage myopathy, RER



Clinical Presentation



Disease Forms/Subtypes




• Polysaccharide storage myopathy: Most common in Quarter Horse, Paint, Appaloosa, Arabian, Morgan, Warmblood, Saddlebred, Standardbred, and Draft-related horses and ponies but can occur in any breed (including Thoroughbreds)


• RER: Described in Thoroughbreds with evidence of a calcium handling defect; not confirmed in other breeds



History, Chief Complaint


Variable. Severe cases can exhibit reluctance to move, stretched-out stance, sweating, hard or swollen muscles, muscle pain on palpation, recumbency, and red-brown urine. Less severe cases may have performance, gait, stamina, or attitude problems under saddle or in harness.



Physical Exam Findings




• Muscles may be hard, swollen, or painful, especially the back and gluteal muscles. Back pain or stiff gait, particularly of pelvic limbs, may be evident.


• Severely affected horses may be recumbent.


• Physical findings may also be normal.



Etiology and Pathophysiology




• Polysaccharide storage myopathy: Linked to abnormal carbohydrate metabolism and an alteration in the skeletal muscle glycogen synthase 1 (GYS1) gene, but exact pathophysiology is not known.


• RER: Possible sarcoplasmic reticulum calcium handling defect, but exact pathophysiology is not known.


• Pasture-associated rhabdomyolysis: Possible as yet unidentified plant toxin, but rhabdomyolysis can also occur while on pasture in horses that are severely selenium deficient, in horses exposed to known myotoxins (eg, ionophores, Cassia occidentalis), and in horses with underlying myopathy (polysaccharide storage myopathy or RER).

< div class='tao-gold-member'>

Related posts:

  1. Aggressive Stallion Behavior
  2. Aflatoxin Toxicosis
  3. Biliary Atresia
  4. Black Widow Spider Toxicosis

Stay updated, free articles. Join our Telegram channel
Tags:
Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Rhabdomyolysis

Full access? Get Clinical Tree
Get Clinical Tree app for offline access