Path 2 - Muscles - Degenerative Myopathies

sihirlifil's version from 2017-04-29 15:00

Nutritional / Exertional / Toxic / Electrolyte / Ischemic / Endocrine

Question Answer
Deficiency of what causes degenerative myopathy?Vit E/Se
What are vitamin E and selenium essential for?Vitamin E: antioxidant
Selenium: neutralization of free radicals which cause lipid peroxidation
What does nutritional myopathy look like? Clinically?Hyaline degeneration and necrosis of striated muscles
Stiffness, recumbency, sudden death (with cardiac muscle involvement)
Pathogenesis of nutritional myopathyFree radicals attack lipid membranes --> Lipid peroxides --> destroys cell membranes --> influx of Ca into cytosol & mitochondria --> segmental necrosis
What type of necrosis is nutritional myopathy?Multifocal multiphasic
Gross lesions of nutritional myopathyBilaterally symmetrical segmental necrosis, calcification & regeneration
Pale, inelastic, friable, dry; patchy white streaks (calcium salt deposition)
Who (& where) does nutritional myopathy affect? (spp diff)Pigs: selective necrosis of Type I (intercostals, diaphragm, tongue, heart)
Calves: LV
Sheep: RV
Microscopic lesions of nutritional myopathyZenker's (flocculant) degeneration
Loss of striation
Fiber framentation
Proliferation of myosatellite cells
Nutritional syndromes: (7)*White muscle disease* of calves
Stiff lamb disease in sheep
Porcine vit E/Se responsive disease complex
Pansteatitis in cats
Brown dog gut
Masticatory myopathy and polymyopathy in foals
Muscle necrosis and steatitis in rabbits
White muscle disease of calves: 3 conditionsCardiac: acute heart failure
Locomotory: paralysis, recumbency
Pulmonary: dyspnea
Stiff lamb disease:Congenital, lesions develop in utero (tongue, neck) / Acquired (shoulders, thigh)
Porcine vit E/Se responsive dz complex: 5 conditionsMulberry heart disease
Arteriolar degeneration (edema)
Gastric ulceration
Hepatosis dietetica
Yellow fat disease
Pansteatitis in cats:Yellow fat disease (fat necrosis, granulomas)
Brown dog gut:Deposition of ceroid-like pigment in smooth muscles (spleen, small intestine)
Masticatory myopathy and polymyopathy in foals:Calcification (masticatory, tongue) & death from aspiration pneumonia
What is exertional myopathy? Lesions?Diseases resulting in severe muscle degeneration following strenuous exercise
Type II glycolytic fibers affected
Pathogenesis of exertional myopathy?Rapid utilization of glycogen, lactic acid accumulation, alteration in protein structure (denaturation from increase in local heat), water loss (interstitial edema), compressive circulatory disturbances and ischemia, myoglobinemia/uria (damage tubules)
High intracellular Ca = hypercontraction, hyaline degeneration, necrosis
Syndromes of exertional myopathy (3)Azoturia, tying-up in horses
Cattle: azoturia-like syndrome
Wildlife: Capture myopathy
What is azoturia? Aka? Clinical picture?Equine paralytic myoglobinuria, Monday morning disease, sacral paralysis, exertional rhabdomyolysis
Sudden onset of stiff gain (muscle weakness), reluctance to move, swollen muscle groups, sweating, myoglobinuria, acidosis, death from cardiac or renal failure
Etiology of azoturiaMuscle lactic acidosis, electrolyte abnormalities, vit E/Se deficiency, hypothyroidism, forced exercise after period of rest without restricting feed, EPSSM
Lesions of azoturiaBilateral moist, swollen, hemorrhagic quads, gluteals (& cardiac if severe)
Hyaline degeneration, necrosis --> fibrosis, atrophy, muscle pallor
Myoglobinuric nephrosis: dark-black kidneys
Sequelae of azoturiaDeath from CARDIAC and RENAL injury
Recovery and repeated episodes --> atrophy
Recovery w/ regeneration
What is tying-up?Less severe version of azoturia
Mild rhabdomyolysis
Azoturia-like syndrome: who does this affect? Associated with?Zebu or Wild
Handling, transportation over long distances, crowding
Exertional myopathy of dogs: who specifically? Following?Greyhounds
Following intense muscular exertion
**Capture myopathy: what is going on?Wild animals, birds following capture, translocation, chase, struggle
Pronounced acidosis
Lesions: Bilateral pale, edematous, degeneration, hemorrhage, ruptured tendons, myocardial injury --> death from CHF
**Toxic myopathy: causes?Ionophores
Phytotoxins, gossypol, drugs/chemicals, mycotoxins
**Exertional rhabdomyolysis aka?Exertional myopathy, azoturia, setfast, black-water, Monday morning disease, tying-up
Toxic myopathy: basis for susceptibility?Muscle mass, high blood flow, mitochondrial energy metabolism; selective binding of mycotoxin
Toxic myopathy: lesionsIll-defined pale streaks of myocardium, skeletal muscle
Extensive muscle necrosis --> myoglobinuria
What are ionophores? who are most susceptible?Feed additives for poultry, ruminants for antibiotic & growth enhancement
Horses most sucseptible > dog & pig > sheep & goat > cattle > poultry
Pathogenesis of ionophore toxicityFacilitate movement of cations across cell mb --> disrupt equilibrium --> Ca overload --> necrosis (skeletal and CARDIAC)
Death from CV shock and collapse
Ionophore toxicity: type of necrosis?Monophasic MULTIfocal segmental
Pallor, regen, myocardial fibrosis
Toxic plants:Cassia occidentalis (coffee senna)
Karwinskia hulmboldtiana (coyotillo)
Eupatorium rugosum (white snakeroot
Cestrum diurnum
(Other vit D-analog-containing plants)
What is gossypol? Who does it affect?In cotton seed meal (feed additive in dairy cattle)
Muscle necrosis in dogs/pigs
Electrolyte-related myopathies (4)Hyperkalemia (HYPP)
**Hypokalemia in CATTLE: what happens?Profound weakness and recumbency
Anorexia, ketosis; glucocorticoid administration; IV admin of glucose or insulin (increases flow of K into cells)
Decreased K concentration in muscles; abnormal cardiac conduction
**Hypokalemia in CATS: what happens?Generalized weakness, neck ventroflexion

Decreased dietary intake, CRD increases urinary excretion, 2ry to GI disease, inappropriate fluid therapy, hyperthyroidism (increases activity of Na-K-ATPase)
Hyperpolarization of cell membrane, myofiber necrosis, abnormal cardiac conduction, chronic interstitial nephritis
**HypERnatremia in CATS: what happens?Abnormal energy metabolism, vasoconstriction, ischemia
Myofiber necrosis and regeneration
**Hypophosphatemia in catle: what happens?Profound muscle weakness, CNS signs, hemolytic anemia
Dietary, vomiting, diarrhea, hypercortisolism, renal disease, diuretics
Myocardial & skeletal muscle necrosis, ischemic (recumbency)
**What is porcine stress syndrome (PSS)? what happens?Aka malignant hyperthermia, pale soft exudative (PSE) pork, back muscle necrosis
Inherited in certain breeds
Respiratory and metabolic acidosis
myoglobinemia, hyperkalemia, high blood lactate, hyperthermia, cardiovascular collapse
Stresses contributing to PSS (8)Fighting, exercise, crowding, transport, handling, overheating, slaughter, halothane anesthesia
**Pathogenesis of PSSDefect in uptake, storage, release of Ca from sarcomere: high intracellular Ca, increased glycolysis, buildup of lactate and body heat
Hypercontraction and denaturation --> necrosis; intracellular water moves to interstitium --> wet, exudative muscles
Is PSS restricted to pigs with a gene mutation?No- any pig can suffer from PSS if stressed enough
More prone if carry mutant Hal gene
**PSS: which receptor is mutated? what does it lead to?Ryanodine receptor (calcium release channel in sarcoplasm)
Leads to changed membrane characteristics, uncontrolled calcium release (hypercontraction, heat production)
**PSS: lesions?Type II fibers affected
Back muscle necrosis, edemaPale, soft, exudative PSE
Pulmonary edema, hydrothorax, ascites
**Ischemic myopathy: Compartment syndrome in who?Deep pectorals of poultry (turkey, chicken)
Exertion, flapping of wings, necrosis of supracoracoid m.
Ischemic myopathy: Downer syndrome in who? why?Mature animals (cow > sheep, pigs, horses)
Necrosis of ventral & limb musclces, follows prolonged recumbency
Ischemic myopathy: Aortic-iliac thromboembolism: who? what does it look like?Cats (saddle thrombus) > horses
Vascular occlusion: pain, paresis, pulselessness, poikilothermy, pallor
**Endocrine myopathy: Hypothyroidism- what happens?Generalized weakness, atrophy, megaesophagus
Decreased thyroid hormone (muscle metab), peripheral neuropathy (axonal degeneration = denervation atrophy)
Selective for Type II fibers
**Endocrine myopathy: Hypercortisolism- what happens? lesions?Weakness, atrophy of Type II fibers
Increased cortisol = denervation atrophy with regeneration
Atropy, bilateral adrenocortical hyperplasia, +/- tumor in pituitary/adrenals

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