Muscle Diseases Flashcards
What are the symptoms of Equine Rhabdomyolysis Syndrome and why do these symptoms occur?
muscle cramping/ pain that occurs usually during or following exercise due to the breakdown of striated muscle fibres at rest
What is Equine Rhabdomyolysis Syndrome also known as ?
Monday Morning disease
Does Equine Rhabdomyolysis Syndrome need treating?
If acute- maybe if an emergency but can self resolve
Investigate cause if episodes are recurring
What may we see in the blood of a horse with Equine Rhabdomyolysis Syndrome and why?
Increased creatine kinase and aspartamino transferase (AST)- these enzymes are associated with normal muscle function, when muscles get damaged they’re released into the extracellular space into circulation
In horses with Equine Rhabdomyolysis Syndrome we see dark reddish tinged urine, why?
How do we differentiate this from bloody urine?
Due to high protein content due to muscle breakdown- to differentiate this from bloody urine we just spin the sample and observe if any sediments lay in the bottom- if they do then these are RBC’s
A horse has increased AST but no increase in Creatine Kinase, what does this suggest?
Hepatic disease- BOTH CK and AST need to be high to indicate muscle breakdown
How do we treat Acute Exertional Equine Rhabdomyolysis Syndrome?
Analgesics - Opioids preferred
IV or oral fluids to support kidney processing the extra protein
What causes ACQUIRED Equine Rhabdomyolysis?
Overexertion e.g. muscle overlengthening, metabolic exhaustion (no glycogen in the muscle)
Electrolyte imbalance
Infectious causes
What can cause INHERITED Equine Rhabdomyolysis?
Defective calcium regulation (occurs in Thoroughbreds in the USA)
Polysaccharide storage myopathy
How do we prevent Recurrent Equine Rhabdomyolysis (caused by defective calcium regulation)?
Oral dantrolene- a calcium release channel blocker- give before exercise
[careful not to give too much- still need to release some calcium lol]
What causes Polysaccharide storage myopathy?
Missense mutation in glycogen synthase (the enzyme responsible for breaking down glycogen branches/ cross links) causing increased activity in skeletal muscle leading to muscle atrophy/ weakness
How would we diagnose Polysaccharide storage myopathy? (2)
DNA test for the mutation by submitting blood/ hair pluck
Muscle Biopsy shows accumulation of glycogen in cells
How do we manage Polysaccharide storage myopathy?
High Fat, Low carb diet (fat used for energy- less glycogen breakdown)
What is Coccygeal Muscle Injury caused by?
How is it treated?
Usually occurs in working breeds after lots of swimming, exercise, cold
Treat with NSAIDs and rest
What are the three locations of Ion Channelopathies that cause muscle disease?
Sodium pump
Ryanodine Receptor
Calcium ATPase pump
Give an example of a pathology in the Sarcolemmal sodium pump that would cause muscle disease?
Hyperkalaemic Periodic Paralysis- sodium channel stays open causing sodium to rush in > membrane depolarises leading to contraction & then paralysis
Give an example of a pathology in the Ryanodine Receptor that causes muscle disease?
Malignant Hyperthermia happens when animals are given dissociative anaesthetics, the drugs induce an opening of the Calcium receptor so calcium flows out
Give an example of a pathology in the Calcium ATPase receptor that causes muscle disease?
Congenital Pseudomyotonia- impairs the relaxation of skeletal muscles because calcium cannot go back into the sarcoplasmic reticulum after contraction
How do cell signalling defects effect the muscles?
Give an example.
Mutations in the expression of Myostatin which is the protein that restricts excessive muscle growth can cause excessive muscles e.g. Belgian Blue cows, Bully racing whippets
What is Fibrotic Myopathy and what causes it?
Abnormal scar tissue forming in the muscle ()most commonly the hamstring) - caused by muscle tear, IM injections
What is the tell tale sign of Fibrotic Myopathy in horses?
Characteristic gait- foot slaps on the ground as the fibrous tissue in the muscle acts like a bungee chord
What pathology is associated with lipid accumulation in a muscle biopsy and what causes it?
Atypical Myopathy- mitochondria poorly metabolising fatty acids OR ingestion of plant toxin (Hypoglycin A) found in elder or sycamore trees
How do muscular dystrophies cause muscle disease?
Proteins known as Dystrophin associated glycoprotein complexes line the muscle fibres- patients with muscular dystrophies have an out of frame deletion of this protein that causes it to lose function
Theoretically how could we treat Duchenne Muscular Dystrophy with gene editing?
Use CRISPR to cut and remove so that the exons that had the mutation fit together and become functional again
