Pathology - Test 2 (Muscle Pathology)

Front 1

muscular dystrophy

Back 1

-congenital, inherited

-mscles are pale and atrophic due to progressive degeneration, necrosis and loss of myofibers

-replacement of these with fat and fibrous tissue

Front 2

myotonia

Back 2

inherited, prolonged contration of muscles

-muscles contract for several seconds and produce dimpling of skin
-muscle may be enlarged and prominent
-mostly in goats

Front 3

spastic paresis

Back 3

inherited disease of cattle in which the rear limbs are straight at the hock and unable to flex

Front 4

myasthenia gravis

Back 4

disease of dogs where dogs become weak and fatigue easily with exercise

(1) congenital = inherited deficiency in the numbers of Ache receptors

(2) acquired = caused by antibodies against Ache receptors

-muscles are normal grossly

Front 5

Polysaccharide storage myopathy

Back 5

-in horse (inherited)
-defect in carbohydrate metabolism
-muscles may have necrosis or atrophy

Front 6

What is present microscopically in horses with PSM?

Back 6

-amylopectin in muscle fibers

Front 7

Hyperkalemic periodic paralysis

Back 7

-inherited in horses
-defect in Na channels in muscles that result in hyperkalemia

-transient muscle spasms followed by flaccid paralysis

-no gross of microscopic lesions

Front 8

Four types of atrophy

Back 8

(1) denervation atrophy
(2) disuse atrophy
(3) cachexia
(4) endocrine atrophy

Front 9

denervation atrophy

Back 9

-common due to damage to nerve supply from trauma, inflammation, neoplasia
-atrophy is quick in a few weeks
-affects type 1 and 2 myofibers

Front 10

Disuse atrophy

Back 10

-when muscles are not used
-not as noticable and slower

Front 11

Cachexia

Back 11

disease of malnutrition results in protein mobilization from muscle to supply energy

Front 12

endocrine atrophy

Back 12

in hyperadrenocorticism and hypothyroidism
-presents as generalized weakness
-atrophy NOT visible grossly, but microscopically

Front 13

hypertrophy

Back 13

response to increased workload (racing animals)
-compensatory response when muscle is damaged
-visible microscopically

Front 14

Give the five general categories of causes of muscle necrosis.

Back 14

(1) nutritional
(2) toxic
(3) exertional
(4) ischemia
(5) myositis

Front 15

What is the gross appearance of necrotic muscle?

Back 15

-paler, swelling due to edema
-tan to white streaks are present which indicate mineralization of necrotic myofibers

Front 16

What do tan to white streaks in muscle mean?

Back 16

-mineralization of necrotic myofibers

Front 17

What are the rules for muscle degeneration?

Back 17

(1) if BM is intact, complete myofiber regeneration occurs and repair of muscle
(2) if BM is not intact, leads to repair by fibrosis

Front 18

What type of vitamin deficiency causes muscle necrosis?

Back 18

selenium/vita E

-in young ruminants

Front 19

What is the clinical signs of nutritional muscle necrosis?

Back 19

-stiff gait (rear limb muscles, bilateral and symetrical)
-those with cardiac necrosis may become recumbant and die with respiratory failure
-other muscles = diaphragm and tongue and neck in sucking animals

Front 20

Name three toxins that cause muscle necrosis.

Back 20

(1) monensin - coccidostatic drug for poultry, but toxic to monogastrics (horses esp)
(2) Cassia occidentalis - poisonous plant in south; signs in ruminants after a frost; weakness, diarrhea, and stumbling, minimally white streask
(3) adriamycin - anticancer drug in sm. animals-->cardiac muscle necrosis

Front 21

Name three forms of exertional muscle necrosis.

Back 21

(1) exertional rhabdomyolysis
(2) malignant hyperthermia
(3) capture myopathy

Front 22

exertional rhabdomyolysis

Back 22

-in horse (Tying up), inherited
-exercise and is seen after a rest after remaining on full high carb rations
-underlying polysaccharide storage
myopathy
-gluteal and lumbar muscles affected
-red urine (Azoturia)

Front 23

malignant hyperthermia

Back 23

-hyperthermia, metabilic acidosis, muscle rigidity, and high mortality
-muscle is pale, soft and edematous in shoulder, loin thigh and back
-inherited due to defect in ryanodine receptor (a Ca release channel)
-in pigs, horses, and dogs

Front 24

What species most commonly develops malignant hyperthermia - what is another name for it?

Back 24

pigs

-porcine stress syndrome
-develop under halothane anesthesia

Front 25

List three causes of ischemia that lead to muscle necrosis.

Back 25

(1) compartment syndrome
(2) downer syndrome
(3) crush syndrome

Front 26

muscle ischemia

Back 26

-affects muscles in a localized area - distinct grossly

-outcome is based on duration
-long periods of ischemia lead to more necrosis and repair by fibrosis

-ischemia of a day can lead to infarction of whole muscle

Front 27

compartment syndrome

Back 27

leads to ischemia
-occurs in muscles enclosed by a fascial sheath or bone and sheath
-muscle is not able to expand during exercise and pressure leads to occlusion of the blood supply

Front 28

downer syndrome

Back 28

occurs in recumbent animals - leads to pressure necrosis

Front 29

crush syndrome

Back 29

-with severe trauma where muscle is lacerated
-subsequent edema, inflammation and hyperemia lead to swelling and increased pressure in the muscle

Front 30

What is myositis caused by?

Back 30

Clostridial infections

Front 31

What two types of myositis are there?

Back 31

(1) Black leg - C. chauvoei
(2) malignant Edema - C. septicum

Front 32

Black leg

Back 32

-affects young, feeder animals (cattle and sheep)
-in good nutritional condition
-NO wounds
-pelvic and pectoral girdles most affected
-sudden death without clinical signs

Front 33

Malignant edema

Back 33

-confined animals, secondary to a wound caused by trauma
-begins as cellulis and spreads
-crepitus, pail, not moist

Front 34

What do the lesions of myositis look like grossly?

Back 34

-black leg and malignant edema are the same
-muscle is pale and dry and has an odor of rancid butter
-sanguinous edema fluid and gas bubbles

Front 35

What four types of myositis are there?

Back 35

(1) clostridial
(2) masticatory myositis of dogs
(3) parasitic
(4) dermatomyositis

Front 36

What type of disease is masticatory myositis of dogs?

Back 36

-immune mediated in which antibody is directed against unique type 2M myosin in the muscles

-also called eosinophilic myositis or atrophic myositis

Front 37

What happens to dogs that have masticatory myositis?

Back 37

-have recurrent attacks of pain and mandibular immobility

-muscles are swollen, dark and streaked with hemmorhage
-later, they become atrophic, pale and fibrotic

Front 38

Name four types of parasitic myositis.

Back 38

(1) Toxoplasma/Neospora - dogs
(2) Sarcocystis - ruminants
(3) Cysticerci - herbivores (ruminants and pigs)
(4) Trichinella - nematode in pigs

Front 39

rhabdomyoma

Back 39

very rare
-congenital in heart of lambs and pigs, larynx of dogs
-pale tan to white and firm
-benign, but often cause death because of location

Front 40

Rhabdomyosarcoma

Back 40

rare, very malignant
-pale tan with hemorrhage and necrosis
-urinary bladder of dogs less than 2

Front 41

Leiomyoma

Back 41

-uncommon, benign tumor of smooth muscle in GI tract of small animals
-MOST common tumor of femal repro tract of small animals
-firm, tan and form discrete nodules within the lumen

Front 42

Leiomyosarcomas

Back 42

-1/10 as often as leiomyomas
-firm, tan and nodular
-metastasis is slow