Pathology of Skeletal Muscle - Part 2

Question 1

Arthrogryposis is a _______
condition in ______ fetuses
(______ & _____) and _______
characterized by rigid ______ and ____ in abnormal grotesque
positions. Unclear etiology but usually
associated with _________
abnormalities of the _____ system
(e.g.: spina bifida, syringomyelia etc.,).

What is the most common cause? What are some less common causes?

Answer 1

congenital, aborted, cattle, sheep, stillborns, joints, limbs, developmental, nervous

Lack of innervation (denervation), leading to muscle hypoplasia, is the most common cause.

May be the result of ingestion of toxins or in-utero viral infections (e.g. Akabane disease, Cache Valley fever and blue tongue cause clusters of arthrogryposis in cattle and sheep)

Illanes notes: Easy to diagnose b/c animals usually have ? hair. Associated with developmental anomalies in CNS –> lack of innervation of muscles in limbs. Can also be associated with toxins. If you have several animals born with this issue, may have to think that this may not be an isolated incident. A viral infection may cause this, or rule out a viral toxin from a plant.

Question 2

This animal is suffering from?

Answer 2

Arthrogryposis

Question 3

Muscle Dystrophy is _______ determined, ________ degenerative disease of muscle. Regenerative attempts are _______ or _____.
Described in multiple species but most commonly occurs in ______ ______. The ______, _____, and ____ are animal models for Duchenne’s muscular dystrophy –> affected animals
and people lack _______, a _______ protein that ______ muscle and protects it from _______.

Answer 3

genetically, progressive, inadequate, absent, golden retrievers, mouse, dog, cat, dystrophin, cytoskeletal, strengthens, injury

Question 4

Explain why muscular dystrophy is most commonly found in golden retrievers compared to other dog breeds?

Answer 4

An X-linked dystrophin gene defect has been identified in Golden Retrievers.
Similar disorders have been diagnosed in other breeds including Irish Terriers,
Samoyeds, Labrador Retrievers, Rottweilers, Dalmatians etc.) Muscle
degeneration/ necrosis and fibrosis lead to progressive clinical disability in young
male dogs. Dogs are considered the best animal model for human muscular
dystrophy. The heart and esophagus are also involved (progressive
cardiomyopathy and megaesophagus).
Note muscle wasting and a characteristic outward rotation (splaying) of fore limbs
(image). Death may be the result of aspiration pneumonia or cardio-respiratory
failure.

Illanes notes: Very well documented in golden retrievers. Outward rotation is very characteristic. Also reported in other breeds, but GR very common.
Present in skeletal muscle and heart, leading to significant cardio myopathy and can die of cardio respiratory failure. Diaphragm is involved. Esophagus of dogs there is skeletal muscle as well so you can also have megaesophagus. Possible result of megaesophagus –> Aspiration pneumonia. Animal usually has to be euthanized.

Question 5

This animal is suffering from?

Answer 5

Golden Retriever suffering from muscular dystrophy

Question 6

Equine Polysaccharide Storage Myopathy (EPSSM) is an ________ disease reported mainly in what horse breeds?
Some animals are ________, others exhibit ____ abnormalities (_____
limb lameness) and ______ muscle mass. Microscopically there is an accumulation of ____ ______ material
(_______) in ______ muscle associated with
degeneration/ necrosis of type ___ fibers.
• An underlying ______ _____ disorder is also suspected.

Answer 6

inherited, QH, Arabian horses,
Morgans, Ponies and draft-related breeds.
asymptomatic, gate, hind, reduced, PAS positive, polysaccharides, skeletal, II, carbohydrate metabolic

Illanes notes: mainly effects quarter horses.
Only thing you can see if an animal is effected or suspected of this condition, take muscle bipsy and see accumulation of poly saccharides. PAS stain will show accumulation of polysaccharides in skeletal muscle and the condition will result in degeneration and necrosis of type 2 fibers b/c undergo glycolytic metabolism. May not present clinical signs, some may have lameness, muscle fibrilation? sometimes. Important condition in horses. Etiology is not completely elucidated.

Question 7

1. Porcine Stress Syndrome (porcine malignant hyperthermia
   – pale soft exudative [PSE]pork ) is what type of disorder? What animals does it affect? What mutation does this syndrome cause?
2. What is this syndrome characterized by?
3. What specifically about the animals effected makes them most susceptible to disease?
4. Describe the pathogenesis of PSS.

Answer 7

1. Inherited disorder of domestic pigs (Pietrain, Yorkshire,
   Duroc, Landrace etc.,) – single point mutation in the skeletal
   muscle ryanodine receptor gene (ryr1).
2. Hypermetabolic syndrome characterized by dyspnea, muscle
   rigidity and convulsions, hyperthermia, lactic acidosis,
   hyperkalemia, cardiovascular collapse and death.
3. Heavy-muscle pigs are more susceptible to clinical disease,
4. Pathogenesis related to the uptake, storage and release of Ca
   ions –> the ryanodine receptor is a Ca release channel –> uncontrolled Ca release leads to excessive muscle contraction
   and heat production (hyperthermia).

Illanes notes: Animals with this Ryr1 gene defect there is an uncontrolled Ca release which leads to muscle contraction especially in situations of stress and these animals can develop hyperthermia and die. Can also suffer from seizures. Reported sometimes in slaughter house, because pigs are very smart. Once people knew that this was a genetic defect, they were able to test for it and remove it from the breeding line.

Question 8

Describe the image below

Answer 8

Porcine Stress Syndrome (PSS) – Pale swollen and “wet” muscles (longissimus dorsis)

Extramuscular lesions in pigs that died of PSS are those of acute heart failure: pulmonary edema and congestion, hydropericardium, hydrothorax and hepatic congestion.

Illanes notes: Usually died acutely of acute cardio respt failure, will see pulmonary edema, accumualtion of fluid in pericardial sac, pericardium, and thorax = hydrothorax.

main lesion in muscles.

Question 9

In cases of PSS, muscles commonly affected are
the ?

Answer 9

muscles the back (longissimus dorsis & psoas),
thigh, and shoulders.

Question 10

Microscopically, PSS is characterized by?

Answer 10

Acute myofibre degeneration characterized by interstitial edema, myofiber swelling and fragmentation – PSS, AV as well as segmental hypercontraction with “retraction cap.”

Illanes notes:
Animals do not survive very long. If you look at muscle grossly affected, you will see acute muscle degeneration. Swelling of muscle fibers, loss of straitions, see fragmentation of cytoplasm of cells, presence of interstitial edema. See image to right. Retraction caps due to hyperthermia from muscle contraction (see image above).

Question 11

Nutritional Myopathy (White Muscle Disease)
1. Is the result of?
2. Primarily a disease that affects?
3. What parts of the body are mainly effected?
4. Most common in what species?
5. White Muscle Disease can coexist with what other disease in pigs?
6. Describe the pathogenesis of this disease.

Answer 11

1. The result of Vit E/ Se deficiency
2. Primarily a disease of young animals; Usually affects the rapidly growing and best nourished animals in the herd/ flock
3. In addition to skeletal muscle the heart may also be affected
4. Most common in sheep, cattle and pigs
5. In pigs can co-exist with other Vit E/ Selenium syndromes (hepatosis dietetica, mulberry heart disease).
6. Pathogenesis: Oxydative damage (lipoperoxydation of cell membranes)
   due to deficiency in oxygen-radical scavengers: Vit E and selenium- containing enzymes like glutathione peroxidase/ reductase.

Illanes Notes: Not confined to ruminants and pigs, but seen in these animals more commonly.
Lesions produced in heart (marble heart disease), liver (hepatosis diatectica), in pigs.
Normally affect young animals growing rapidly. high metabolic rate. normal metabolism results in normal oxidative damagebut we have vitamin e and seleniumthat protect us from further damage and myofiber degeneration of skeletal muscle and heart. Animals affected may be lame, reluctant to move. In ruminants, may see respiratory distress associated with involved of diaphgram.

Question 12

Calcification is a frequent outcome of _____ ______ in cases of
Vit E/ Se deficiency –> ____ muscles –> “_____ ______ disease”

Answer 12

muscle degeneration, pale, white muscle

Question 13

Nutritional Myopathy: White Muscle Disease
1. In cattle, WMD primarily affects?
2. Common clinical signs?
3. What muscles are commonly affected?
4. In cases in which skeletal muscle lesions predominate they are most severe in?
5. What muscles are most affected in nursing calves?

Answer 13

1. In cattle primarily affects calves 1-6 months of age.
2. Stiffness and dyspnea are common clinical signs.
3. Intercostal muscles and diaphragm (type I fibers) are often affected even when there is little involvement of other skeletal muscles.
4. Muscles of the thigh and shoulders.
5. In nursing calves, the tongue and neck muscles are often affected (more active muscles –> Increase production of free radicals).

Question 14

Describe the image below

Answer 14

White Muscle Disease
In young calves or lambs, muscles more affected ar eneck muscles and tongue muscles because they are used for suckling. The more active muscles are the ones that are more suscpetible to oxidative damage and you will find lesions here.
Muscle is more pale, granular appearance (mineralization - gritty sensation due to calcification).

Question 15

Describe this image below

Answer 15

Foal nutritional myopathy

Question 16

Describe this image below

Answer 16

Nutritional myopathy
manifestation of injury in muscles are the same:
myofiber swelling, loss of straitions, fagmentation of sarcoplasm, areas of regenerative ?, etc.

Question 17

Describe this image below

Answer 17

Nutritional myopathy
Vitamin e and selenium deficiency can produce lesions in heart. If you see a lamb wiht this nutritional myopathy and it has lesiosn in the heart, for some reason are confined to the right side as seen here. Pale muscle in the right side, slightly raised whitish region of mineralization.

Question 18

Describe the image below

Answer 18

Calf, “white muscle disease”
In calves, region affected is on the left

Question 19

Describe the image belowmuscle damage

Answer 19

Calf, 2 days-old, heart, nutritional myopathy

may be born from vitamin e/selenium deficient mothers, born with condition, and then when move around develop oxidtative muscle damage and die.
selenium deficient soil –> vitamin e to pregnant cows –> incidence of condition decreased.

dystrophic mineralization; von kossa stain can highlight caclium mineralization; looks like dark brown or black. Very easy to recognize when use this stain.

Question 20

Exertional Myopathies are a group of diseases characterized by ______ ______ initiated by _____ ______ (exercise, stress) in which the underlying cause is ______ or _____ ______. Such activity may be intensive or exhaustive but
in susceptible individuals exertional myopathy
may occur with only ______ _____. Some believe that there is a _______ component

Answer 20

muscle damage, muscle activity, unknown, poorly understood, minimal exercise, genetic

Question 21

List and describe 5 examples of Exertional Myopathies

Answer 21

HYPP
Exertional Rhabdomyolysis
Greyhound and racing sled dog myopathy
Capture myopathy
Compartment syndrome

Hyperkalemic periodic paralysis (HYPP). Inherited condition.
Affected horses are descendants of a famous Quarter Horse stallion named Impressive. Well defined muscle groups rewarded in halter competitions. Underlying defect:
alteration in muscle sodium channel (leading to release of
potassium in the bloodstream and extracellular space
transient muscle spasms (myotonia), could lead to flaccid
paralysis and even death.
• Exertional Rhabdomyolysis (azoturia, tying up, paralytic
myoglobinuria, Monday morning disease).
• Greyhound & racing sled dog myopathy – similar to equine
rhabdomyolysis.
• Capture Myopathy
• Compartment Syndrome

Question 22

Describe the image below

Answer 22

HYPP = observed in animals that are descendents of the stallion, impressive. This horse had very rounded muscles and he received many awards. Animal affected with this, muscle fasciulations, spasms, etc. Some horses can develop problems that lead to paralysis and death. Widespread in QH population.

Question 23

1. Equine Exertional Rhabdomyolysis is also known as?
2. What types of horses are more susceptible to severe disease?
3. Describe the etiology of this disease.
4. What is commonly seen in affected horses?
5. What is their strong evidence of?
6. Why was this also called monday morning disease?
7. Muscles commonly affected?
8. Elevated levels of?
9. What is the most common cause of death?

Answer 23

1. azoturia, paralytic myoglobinuria, Monday morning disease.
2. Heavy horse breeds are more susceptible to severe disease
3. Unclear etiology but appears to be multifactorial
   (overexertion, exhaustion, dietary imbalances
   including electrolyte depletion and low Se/ Vit E levels may be implicated).
4. Underlying metabolic myopathies like equine
   polysaccharide storage myopathy (EPSSM) seem
   common in affected horses.
5. Strong evidence for a genetic predisposition
6. People thought it was associated with high carb diet during weekend and a lot of glycogen stored in muscles and then they start working hard on monday, glycogen was breaking down leading to lactiv acidosis but then realized it was multi facotrial in addition to nutritional factors but also vitamin e and selenium deficiency.
7. Gluteal, femoral and lumbar muscles are
   commonly affected; swollen and rigid
   (board-like consistency)
8. Elevated levels of CK and AST (Aspartate
   Aminotransferase)
9. Myoglobinuric nephrosis is the most
   common cause of death. Dgeneration, necrosis of muscles especially in hind limb, lumbar area –> release of myglobin –> nephrotoxic –> kidnney damage and can be cause of death in some horses.

Question 24

Describe the image below

Answer 24

Exertional rhabdomyolysis
dark red = areas of hemorrhage

Question 25

Describe the image below

Answer 25

Exertional rhabdomyolysis
muscle swelling seen here

Question 26

1. Describe Capture Myopathy
2. What can be seen grossly?
3. What species is this pathology most commonly seen in?

Answer 26

1. Acute, often fatal disease seen most often in
   wild mammals and birds following strenuous
   physical activity (exertion) during capture or
   transport.
2. Lesions: Muscle degeneration-necrosis-
   hemorrhage; occasional ruptured tendon;
   myoglobinuric nephrosis may occur.

Seen most often in wildlife. Follows an episode of either being captured for translocation or during strenuous exercise.
Especially in hind limbs
rupture of tendons, achilles, can also develop myoglob like horses suffering from rhabdomyoysis,.

Question 27

Compartment syndrome is characterized by ______ damage that occurs in muscles surrounded by ______ ______ (_____ ______ _____) or by ______ and _____ (____-_____ ______) when
subjected to ______ _______ ______.
• Occurs in ?
• In veterinary medicine is primarily observed in the
__________ muscles poultry (_____,_____)
following _____ but vigorous flapping of the wings (_____ _____ myopathy).

Answer 27

ischemic, heavy aponeurosis, connective tissue sheaths, bone, sheaths, non-expandable compartments, moderately vigorous contractions, well-conditioned athletes, supracoracoideus, chickens, turkeys, brief, deep pectoral

Question 28

Describe the image below

Answer 28

Deep pectoral myopathy
all muscle fibers will be at same stage of degeneration or necrosis.

Breast has been opened, discoloration of msucel is the supra muscle. Yellow due to necrosis.

Question 29

Describe the image below

Answer 29

Injection site necrosis
Injections given in area –> depending on drug, amount –> necrosis.
discoloration represent myofiber degeneration and necrosis associated wiht injection site lesion.

Question 30

Traumatic Muscle Injury
Downer syndrome: Represents _________ necrosis of _____ and _____ muscles following prolonged ______. The ______ of the body on a limb tucked under the body for a long period of time results in ______ pressure on the ______ –> _____ –> more ______ –> ______ necrosis. _____ ________ in good body condition are more susceptible.
• Most common in ____ because of their weight,
muscle mass and susceptibility to _______ in which _____ is frequent.

Answer 30

ischemic, ventral, limb, recumbency, weight, increased, vasculature, edema, pressure, ischemic, Large animals, cows, diseases, paresis

Question 31

Describe the image below

Answer 31

Downer cow, muscle lesions
post mortem exam shows dark red discoloration due to muscle degeneration, necrosis, hemorrhage, etc.

Question 32

Describe the image below

Answer 32

Downer cow - ischemic necrosis of thigh muscles
dark red discooration, necrosis, hemorrhage, etc.

etiology: compression of vasculature leads to ischemia and ?

Question 33

1. Traumatic Muscle Injury can occur in what situations?
2. Describe EPAM and crush syndrome

Answer 33

1. Horses under anesthesia, acute trauma such as a HBC
2. Equine Post-anesthetic myopathy: Occurs in 3-
   6% of cases in which general anesthesia is used
   –> different degrees of severity. Crush syndrome: Caused by acute trauma. Pathogenesis and lesions similar to Downer syndrome.

Question 34

Traumatic Muscle Injury is characterized by a sudden increase in _____-________ _________ following ____ (cats, dogs) or falls
in ______ and can result in rupture of the ______.
Spontaneous rupture of muscles in racing _______ and ______ can occur; especially the ________ m.
Tearing of _______ muscles in cattle that do the splits on slippery floors is also common, which results in severe damage that will include damage to muscle fiber ______ ______ (heals by ______).

Answer 34

intra-abdominal pressure, HBC, horses, diaphragm, greyhounds, horses, gastrocnemius, adductor, basement membranes, fibrosis

tearing of adductor –> quality of flooring in dairy because during winter or when cleaning floor cna get slippery, split legs –> adductor damage and sometimes animal might have to be euthanized. will heal by second intenton and replaced with fibrous CT.

Question 35

Malignant Edema (also known as?)
• _____ fatal infection caused by wound infection caused by which bacteria?
• These are gram- ______bacilli to a greater or lesser degree ______, and exist in the environment as ________ _____.
• When they proliferate in _______ they are highly ______ and induce extensive muscle _______
Lesions primarily involve the ______ –> ______, moderate ______, ______ and _______ of the overlying skin
• Histologically?
• Malignant edema is most common in domestic _____ and ______ (most often 2ry to _______ wounds)

Answer 35

Gas gangrene
Acute
Cl. septicum,
Cl. perfringens, Cl. novyi, Cl. sordelli and Cl. chauvoei alone or in
combination.
positive, anaerobic, resistant spores
tissues, toxigenic
necrosis
subcutis, edema, emphysema, hemorrhage, discoloration
Edema, cellulitis, minimal myositis.
ruminants, horses
penetrating

Question 36

1. Black Leg is also known as?
2. Black leg is caused by?
3. Characterized by?
4. Describe the pathogenesis.
5. Most common in?

Answer 36

1. (a.k.a.: black quarter, emphysematous gangrene): Acute, fatal necrotizing myositis of ruminants (mainly cattle)
2. caused by Clostridium chauvoei.
3. Characterized by activation of latent spores in muscle.
4. Pathogenesis: spores in the soil –> ingestion –> spores in muscle (latent) –> muscle injury/ hemorrhage -> local hypoxia –> germination of spores in muscles –> exotoxins –> edema/ myonecrosis –> emphysema –> generalized
   toxemia –> death in approx. 24 hrs
5. Most common in cattle 9-months to 2 years of age

Question 37

Describe the image below

Answer 37

Black leg

In cases of black leg, you may find anmals dead. Acute in many cases.

Muscles affected are in scapula, thigh, etc. You can see and feel a bit of crepidation due to trapping of air bubbles b/c gas accumulation in tissue. may also be warm

Question 38

Describe the image below

Answer 38

Black leg: Necro-hemorrhagic and emphysematous myositis (or rhabdomyositis). Clostridium chauvoei

necrotizing and hemorrhagic myositis.

inflammatory condition caused by bacteria.

in addition to discooration due to discooration and hemorrhage, see air bubbles in between indicative you are probably dealing with emphasymateous myositis as well.

Question 39

Describe the image below

Answer 39

Lesions in large muscle masses (scapular and pelvic girdles, occcasionally in tongue, heart, and/or diaphragm)

heart is also affected here.
inflammatory condition so you will have pericarditis, fibrous exudation, etc.

even though in maj cases, see characteristic lesions in skeeltal muscls, some lesiosn may be confined to tongue, heart, diaphragm.

must look everywhere.

Question 40

1. What disease is a form of parasitic myositis?
2. Where does this disease occur? How do animals become infected?
3. What muscles are affected?
4. Common symptoms?

Answer 40

1. Trichinosis (Trichinella sp.). Important zoonotic disease.
2. Rare in Canada/ USA except in the far North – humans are infected by consumption of incomplete cooked meat from pork, bears or aquatic mammals (debilitating disease with death due to myocarditis).
3. Skeletal muscle is the habitat for the larvae of the nematode T. spiralis or nativa (colder climates) which becomes encysted in the muscle.
   • Muscles of the tongue, the masseter, diaphragm, intercostals
   and ocular muscles are commonly infested.
4. Affected animals are usually asymptomatic.

Question 41

Describe the image below,

Answer 41

Trichinella sp. - skeletal muscle
diaphragm particularly susceptible to this.
take sample of diaphragm and soas muscle; pillars of diapharagm are good sample area. look for larvae.

Question 42

Cysticercosis is a form of ______ myositis and an important ______ disease.
• The cysticercus is the larval stage of a ______ (________ parasite ) –> tapeworm.
• The adult stage is in the ______ of the definite host (______, _____, wild _______). The larval
stage (cysticercus) is in the muscle of the _______ host (____, ______, ______,
_______etc.).
• Cysticercosis in humans is the result of ingestion of _____ ______, not from ingestion of ______.,

Answer 42

parasitic, zoonotic, taenia, Platyhelminth, intestine, humans, dogs, carnivores, intermediate, pigs, cattle, moose, reindeer, taenia eggs, cysticerci

Question 43

Sarcocystosis is a form of ________ myositis: Important and common _______ disease
affecting the ______ muscle of a wide range of animals, specially ______, ______ and ______.
•______-walled cysts filled with _______ within striated muscle
• Carnivores (____,____,_____ _____) are the _____ host.
• Sarcocystosis is often considered an ______ finding (______ or ___ host response).
• Although muscle ______ are not important, the disease is considered by some an important
cause of _______.

Answer 43

Parasitic, protozoal, striated, cattle, sheep, poultry, Thin, bradyzoites, dogs, cats, human beings, definite, incidental, minimal, no, lesions, abortion

Question 44

Other parasites such as _______, which can also cause muscle lesions are mentioned in other
systems (?).

Answer 44

Toxoplasma, cardiovascular, nervous, reproductive etc.,

Question 45

Masticatory myositis is a form of ________ and _______-______ myositis:
• Immune-mediated myositis restricted to the _________ muscles in dogs.
• Eosinophilic myositis and atrophic myositis, previously reported as 2 separate disorders, are now considered to be 2 ends of the spectrum in a single disease (acute and chronic form).
• Unclear pathogenesis – _______ against a unique myosin isoform present in _______ muscles: type ___M myosin
• ______ ______ jaw. Affected dogs are unable to fully open their _____ (_____)

Answer 45

Idiopathic, immune-mediated, masticatory, autoantibodies, masticatory, 2, Swollen painful, mouths, trismus

Question 46

In cases of Masticatory myositis, lesions are _______ and ______
• Muscle _______ or _____ are more marked in the _____ and _____ muscles
• ________ ______ appear to be predisposed.
• Late stages are characterized by marked _______ and _______

Answer 46

bilateral, progressive, swelling, atrophy, temporal, masseter, German Shepherds, atrophy, fibrosis

Question 47

Dermatomyositis is a ______ disease in ______ and ______
• Possible _______ mediated etiology
• The disease is characterized by _______ (?) and myositis (______ muscles).
• Most dogs recover _______.

Answer 47

familial, Collies, Shelties, immune, dermatitis, face, ears, tip of the tail and over bony prominences, masticatory, spontaneously

Question 48

Neoplastic diseases of Muscle
Primary tumors:
• Rhabdomyoma: _______ and generally ______. More
common in _____, ____ and ____. Most originate in the ____ (66%).
• Rhabdomyosarcoma: ______ local behaviour with
frequent _____. Metaplastic rhabdomyosarcomas arising from sites with ___ ____ muscle occur
sporadically (?). Embryonal rhabdomyosarcomas, usually involving the ______ or _____ occur in _____ or ____-_____ individuals.

Answer 48

Benign, congenital, cattle, sheep, pigs, heart, Aggressive, metastasis, no striated, kidney, urinary bladder, meninges, head, neck, young, young-adult

Question 49

Extramuscular lesions in pigs that died of PSS are those of _____ ____ failure: pulmonary _____ and _____, ________, _______ and ______ congestion.

Answer 49

acute, heart, edema, congestion, hydropericardium, hydrothorax, hepatic

Question 50

In cases of PSS, retraction caps form as a result of to ________ from muscle _______.

Answer 50

hyperthermia, contraction