Muscle Pathology

Question 1

5 responses of muscle to injury

Answer 1

atrophy
hypertrophy
necrosis
regeneration
fibrosis

Question 2

what is a denervation atrophy in the horse

Answer 2

laryngeal hemiplegia
left recurrent laryngeal n.
atrophy of left cricoarytenoideus dorsalis

Question 3

signalment and pathogenesis of muscular dystrophy (Duchenne’s) in the dog

Answer 3

young male dogs
X linked dystrophin mutation that leads to marked necrosis (severest in diaphragm) & muscle loss

Question 4

signalment and clinical sign of muscular dystrophy (Duchenne’s) in the cat

Answer 4

young male kittens
marked hypertrophy
bunny hopping gait

Question 5

pathogenesis of malignant hyperthermia (porcine stress syndrome)

Answer 5

ryanodine receptor mutation > unregulated Ca channels > hypercontraction of all striated muscle > hyperthermia and lactic acidosis

Question 6

pathogenesis of hyperkalemic periodic paralysis (HYPP)

Answer 6

horses
delayed Na channel inactivation > excess Na IC & K EC > hyperkalemia > myotonia

Question 7

pathogenesis of equine polysaccharide storage myopathy (EPSSM)

what is a pathognomonic lesion of this

Answer 7

mutation in GSY1 > glycogen accumulation in type 2 muscle > muscle degeneration/necrosis

glycogen inclusion

Question 8

pathogenesis of Myasthenia Gravis

what is it caused by?
what is a common clincial sign?
what test can you do?

Answer 8

inherit defect in ACh receptors at the NMJ > decreased contractions
thymoma
megaesophagus
tensilon test - give anti-AChE

Question 9

pathogenesis of downer syndrome

Answer 9

cows
immobile recumbent animals
increased IM pressure > collagenous venous system > red infarct/ischemic necrosis

Question 10

pathogenesis of compartment syndrome

Answer 10

chickens
vigorous musculature contraction
increased IM pressure > collagenous venous system > red infarct/ischemic necrosis

Question 11

pathogenesis of Corynebacterium pseudotuberculosis

Answer 11

“Pigeon Breast/Fever”
organism in the soil contaminates wound or inoculation from insects > spreads to pectoral m > abscess

Question 12

pathogenesis of C. septicum and C. perfringens

Answer 12

C. septicum - malignant edema
C. perfringens - gas gangrene
wound is contaminated with spores > toxins > local necrosis/toxemia > death

Question 13

pathogenesis of C. chauveoi

Answer 13

black leg
spores ingestion > dormant in muscle until trauma > activation > myonecrosis/toxemia

Question 14

pathogenesis of Actinonbacillus lignieresii

Answer 14

“wooden tongue”
focal trauma to tongue allows infiltration of actinobacillus > granulomatous inflam > regional lymphadenitis

Question 15

what do Neospora caninum, Toxoplasma gondii, and Sarcocystis require

Answer 15

2 hosts - herbivore (intermediate/muscle) and predator (definitive/enteric)

Question 16

sarcocystis can result in what type of myositis

Answer 16

eosinophilic myositis

Question 17

hepatozoon americanum
definitive host?
transmission?
clinical sign?

Answer 17

brown tick
ingestion of tick
pyogranulomatous myositis & periosteal rxn (BONE AND MUSCLE CORRELATE)

Question 18

what parasitic nematode is a “true parasite” that is zoonotic, high importance in pigs and cysts that are resistant to freezing and can survive for 20 yrs

Answer 18

trichonella spp.

Question 19

what two parasites can humans acquire from consuming raw meat

Answer 19

trichonella spp
taenia solium & saginata “beef measles”

Question 20

what is extertional rhabdomyolysis

Answer 20

myofiber damage from exercise stress as the primary cause, can also be due to EPSSM
common in horses

Question 21

equine polysaccharide storage myopathy predisposes to what disease

Answer 21

extertional rhabdomyolysis

Question 22

what is capture myopathy

Answer 22

wildlife species that undergo exertion, hyperthermia, lactic acidosis, myonecrosis and cardiac necrosis

Question 23

what are the 2 types of equine post-streprtococcal myositis

Answer 23

purpura hemorrhagica (type III hypersensitivity)
autoAb against muscle in young quarter horses (type II hypersensitivity)

associated with S. equi equi

Question 24

pathogenesis of canine masticatory myositis

Answer 24

autoAb against type 2M myosin (type II hypersensitivity)
eosinophillic plasmacytic myositis > compartmental syndrome > chronic atrophy/fibrosis (masseter and temporal mm)

Question 25

pathogensis of canine polymyositis

Answer 25

lupus, neoplasia, idiopathic
lymphocytic myositis

Question 26

how can you differentiate between canine masticatory myositis and canine polymyositis

Answer 26

serology of 2M myosin Ab

CMM - eosinophilic plasmacytic
CP - lymphocytic

Question 27

pathogenesis of vitamin E/Se deficiency

Answer 27

deficiency in these antioxidants > increased free radicals > membrane damage > loss of homeostasis & release of Ca > necrosis/mineralization

Question 28

lesions associated with vitamin E/Se deficiency

Answer 28

polyphasic (nutritional)
pallor & necrosis of neck, tongue, diaphragm
pigs “hepatosis dieterica, white muscle disease, mulberry heart disease”
reptiles/birds degenerative encephalopathy

Question 29

what toxins can cause myopathies

Answer 29

ionophores - ruminants/horses
gossypol - pigs
Cassia species, Eupatorium, Karwinski - ruminants

Question 30

ionophores and gossypol have what type of necrosis - monophasic or polyphasic?

Answer 30

monophasic

Question 31

ionophore lesions

Answer 31

monophasic
myocardial necrosis

Question 32

gossypol lesions

Answer 32

monophasic
hepatic necrosis & pulmonary congestion
heart failure

Question 33

Cassia species lesions

Answer 33

cardiac tissue NOT involved

Question 34

where do dogs and pigs get a Rhabdomyoma

Answer 34

dogs - larynx
pigs - heart

Question 35

what is the most common skeletal tumor in although still rare

Answer 35

rhabdomyosarcoma

Question 36

where does the bladder botryoiod “cluster” rhabdomyosarcoma occur in young large breed dogs and what is its behavior

Answer 36

trigone of the bladder
low rate of metastasis
poor prognosis

Question 37

what local extension tumor classically invades muscle

Answer 37

infiltrative lipoma