Final- Muscle Flashcards Preview

Path > Final- Muscle > Flashcards

Flashcards in Final- Muscle Deck (71):
1

You are called out to a farm to investigate a sad scene.....

 

Clinical signs

Around 30% of 2 month old lambs in a mob of 40

Lying on their chest, roll on to their side

Weak, stiff

Die within a few days

What can we do to figure out what the pathological process was that resulted in these signs??

 

You are going to do a euthanize and necropsy an acute disease. You don't want to wait for a natural death because you can get secondary infections etc that will hide the primary pathological process.

 

You are going to examine muscle bellies.

What is abnormal? There are muscles that are paleish white, swollen, firm,  and dry to the touch(not shiny).

A image thumb
2

What is an addition pathological process for Skeletal Muscle?

Biochemical

3

What pathological process is responsible for this apperance(same as the sheep case)?

Q image thumb

Degeneration/necrosis- results in a pale color because more water is coming into the muscle

4

What makes muscles pale other than degeneration/necrosis?

Fig. 15-9 Pathologic changes resulting in pale skeletal muscle.

A, Pale streaks, necrosis and mineralization, degenerative myopathy, canine X-linked muscular dystrophy, diaphragm (left side), dog.
B, Localized pallor, necrosis, injection site of an irritant substance, semitendinosus muscle, cow. The irritant was injected just under the perimysium and caused necrosis and disruption of the myofibers. Some irritant seeped down between the fascicles to cause necrosis, but the fascicles of myofibers are still in place.
C, Overall pale muscle with pale streaks from collagen and fat infiltration, denervation atrophy, equine motor neuron disease, horse. Equine motor neuron disease muscle (right) compared with normal muscle (left). Yellow tint; FAT WHERE YOU HAVE LOST SKELETAL MUSCLE,  GREASY AND YELLOW
D, Enlargement and pallor, steatosis, longissimus muscles, neonatal calf. The majority of the muscles have been replaced by fat.

 

calicification can also do this

Fibrious connective tissue

A image thumb
5

Gross morphological diagnosis =

Q image thumb

BEST ONE: skeletal muscle degeneration and necrosis

 

 

6

What is abnormal about this image?

Q image thumb

Sacroplasm/cytoplasm is vacuolated, condensed, loss of cross striations

 

7

Things myofibers do when they are hurt:

They die:

-  Vacuolation of sarcoplasm

-  Condensation of sarcoplasm (looks hyper-eosinophilic, and lose striations)

-  Nuclear pyknosis

-  Calcification(dystropic)

They regenerate:

-  Internalization of nuclei

-  Macrophages infiltrate

8

What types of causes incite this pattern of degeneration and necrosis?

Q image thumb

Pathology report: polyphasic skeletal muscle degeneration and necrosis( myocytes are in different stages of injury and regeneration vs in others where the myocytes are all in the same stage- monophasic)

This means that there is an ONGOING PROBLEM!

 

Causes of polyphasic lesions:

Ongoing insults

Nutritional deficiency – vitamin E/Se

Ongoing toxicities

Genetic defects in myocyte

structural/metabolic elements

9

How does nutritional deficiency cause this mess?

Q image thumb

Pathogenesis: vitamin E/Se deficiency is needed for enzymes like glutathione peroxidase/reductase causeslack of ability to scavenge free radicals. This causes oxidative damage (lipoperoxidation of cell membranes) --> myocyte injury

 

Free Radicals cause necrosis

10

What would the path report say about this and what was the cause?

Q image thumb

Monensin toxicity in a horse

path report- actue MONOPHASIC skeletal muscle degeneration and necrosis

11

Causes of monophasic lesions

Causes of Monophasic Lesions:

A single insult

Trauma (will be focal at the site of trauma)

Exertion, capture

Toxin – ionophores, plants

(coffee senna)

 

HORSES ARE REALLY SENSTIVE-----USUALLY FROM EATING A RUMINANT RATION

A image thumb
12

Edx

Q image thumb

Monesin Toxicity

13

Our lambs with polyphasic muscle degeneration and necrosis.....

Follow up

You rule out access to toxic plants

Further research – they are from a Se deficient area

You arrange dietary vitamin E/Se supplementation

14

White Muscle Disease

Or Nutritional myopathy

Caused by Vitamin E / Se deficiency

See lesions in the most active muscles- because that is where the most free radicals are

Can see lesions in the heart with this condition and other metabolic/toxic myopathies of skeletal muscle

15

Mdx?

Q image thumb

Heart from a calf with White Muscle Disease (nutritional myopathy from vitamin E/Se deficiency).
MDx: Cardiac myonecrosis.

16

Where else are you going to see white muscle disease?

-heart

- muscles of mastication

- tongue(espesically in suckling animals)

-diaphram

17

Single or multiple episodes

General signs of pain, anxiety, cramping most prominent after exercise

Multiple muscle groups look like this

In a horse

Q image thumb

Exerional rhabdomyloysis(Tying up, azoteria)- necrosis/ lysis of skeletal muscle

ionic events of contraction can produce an adverse enviornment when extreme

may have an underlying metabolic conidtions which predispose such as polysaccharide storage disease

18

What types of causes typically incite this pattern of necrosis?

Q image thumb

Acute Toxicity or Exertion

but NOT trauma because it's mutifocal

19

Q image thumb

“Exertional rhabdomyolysis” (Tying up, azoturia) – necrosis/lysis of skeletal muscle

During periods of exertion

Ionic events of contraction can produce an adverse environment when extreme

May have underlying metabolic conditions which predispose, such as polysaccharide storage disease

20

What other species is seen with foci of skeletal muscle necrosis?

Foci of skeletal muscle necrosis common in sled dogs, also observe in racing greyhounds

Exertional? Vit E/Se deficiency involvement? Underlying myocyte metabolism issue? lactosis, lesions in the heart, myglobin injures the kidneys

Sled dog myopathy – lethal, generalized lesions involving non-locomotory muscles

21

“Azoturia”

“Azoturia” = excess nitrogen in urine
This muscle is from a 1 year old deer with capture myopathy.
Why is the kidney and urine abnormal??

red urine from myoglobin from severe muscle necrosis

A image thumb
22

Capture myopathy

Zoo and wild birds

Exertion, stress during capture/handling/transport

• Anaerobic glycolysis ---->hyperthermia, metabolic acidosis

23

Q image thumb

“Malignant hyperthermia” – another example of a metabolic condition predisposing to necrosis

IN PIGS

muscle bellies are pale and dry

Pathogenesis: inherited defect in skeletal muscle ryanodine receptor==> excessive Ca release and contraction when stimulated ----->heat production and myocyte necrosis

 

stress can set off the receptor

MDx: focal muscle degeneration and necrosis

24

Are the pale streaks in this muscle due to degeneration and necrosis?

A. Yes B. No

Q image thumb

NO because it's fat!!!

25

Does this calf have skeletal muscle degeneration and necrosis?

A. Yes B. No

Q image thumb

B- THIS IS NORMAL IS A YOUNG ANIMAL- it will feel soft

26

Another farm call... 34 of 120 yearlings are dead.

Q image thumb

hemorage- bright red!

necrosis- skeletal muscle- VERY DRY

 

A image thumb
27

What is abnormal about this and what pathological process is responsible?

Q image thumb

Muscles are dark red, swollen, softened/friable, palpable crepitus

degeneration/necrosis, inflammation/repair, and circulatory disorder

edema!

28

What would be on the path report and what would we do to confirm the etiology of this condition?

Q image thumb

Pathology report:
Morph Dx - Acute necrotic and hemorrhagic myositis(primary process is inflammation)
Comments - Gram positive bacilli identified, consistent with Clostridium chauvoei infection Disease Dx - “Black leg”

 

to confirm etiology- culture the muscle

29

If this is just a bacterial infection of muscle(Black leg), why did it kill so many cattle?? And why are we seeing these other lesions?

Pathogenesis: Ingestion of spores leads to dissemination to muscle via blood leads to  latency leads to tissue hypoxia/acidosis leads to bacterial proliferation leads to production of exotoxins leads to myonecrosis and systemic endothelial damage leads to death from septicemic shock

 

YOU ALSO SEE EPICARDIAL PETECHIAL HEMMORRAGE AND SEROUS PLEURAL EFFUSION

30

What triggers outbreaks of Black Leg?

Parturition

Handling - IM meds/vax, marking, shearing,

etc

Trauma during confinement

Soil disturbance

 

You just have to vaccinate!

 

31

Types of causes inciting myositis

Necrotic/hemorrhage–Clostridium chauvoei, C. septicum

Suppurative–pyogenic bacteria

Lymphocytic–immune-mediated; NO  GROSS CHANGE IN THE TISSUE; microscopic dx

Eosinophilic–active protozoal/ parasitic infections, immune- mediated

Granulomatous

32

Q image thumb

 

Suppurative myositis in a horse with Pigeon fever caused by Corynebacterium pseudotuberculosis

33

Q image thumb

Eosinophilic myositis in a cow

weird coloration(lavender, gray-green)---- typical  of eosinophils

 

pathogenesis: parasites- tapeworms, sacrocysts

34

Q image thumb

MDx: Focal suppurative myositis

35

Q image thumb

MDx: Diffuse eosinophilic myositis

 

Major Causes: parasites and immune mediated

Eosinophilic myositis in a dog with “Masticatory myositis” (immune-mediated), active phase

36

Q image thumb

Masticatory myositis

37

What happens in the end stage of Masticatory myositis”

MDx: chronic eosinophilic myositis & Muscle atrophy

atrophy of the temporalis muscle

A image thumb
38

Q image thumb

Exophthalmus due to “Extraocular polymyositis”.
Histological MDx: eosinophilic myositis of extraocular muscles.

autoimmune pathogenesis

39

Q image thumb

Intralesional protozoa in small animal – toxoplasma vs neospora

eosinophilic

40

Q image thumb

Eosinophilic myositis in a cow with Sarcocystis spp. infection

41

Q image thumb

 Sheep esophagus infected with sarcocystis gigantica

 

Some spp. of Sarcocyst you can see grossly. Often do not have eosinophilic response.

42

Q image thumb

Cysticercus ovis in skeletal muscle of a sheep.
MDx: skeletal muscle parasitic cysts. +/-eosinophilic/granulomatous myositis

43

ANOTHER farm call!! .... “downer cow”, can’t send to slaughter, want to make sure no diseases that will affect other animals.

What can we do to determine the pathological process responsible for this presentation?

What is morphologically abnormal/ what is the MDx?

Q image thumb

There are discrete areas of muscle pallor bordered by reddened zones in the pectoral muscle of a cow.

 

MDx: skeletal muscle degenration and necrosis or infart

infart- geometric lesion with well demarkcated borders; also the cow was down, so he was lying on it

 

44

pathogenesis of this?

Q image thumb

Leg

Pathogenesis: recumbency  leads to increased intramuscular pressure leads to poor perfusion leads to  ischemia leads to infarction

Can see a similar lesion post- anesthesia of large animals.

 

pale, dry- arterial

congested like this one- venous

45

Melon headed whale, stranded at Brunswick heads (Gold Coast, QLD), May 2014.

Q image thumb

Path report MDx:
Focal monophasic myonecrosis.

 

Pathology report comment:
Due to infarct given history of beaching? Trauma during transport to Sea World? Capture myopathy? Vs. primary cause of beaching?

Infart due to beaching due to encephalsis

46

Q image thumb

“Compartment Syndrome”

Pathogenesis: rapid muscle growth-----> period of increased circulation (exertional) ---> muscle swelling confined by facia ---->impedes blood supply----> ischemia --->infarction

 

Supermarket chicken breast- chickens bred to put on a lot of breast muscle very fast.

47

Q image thumb

MDx: Intramuscular hemorrhage
Cause: trauma (esp penetrating wounds, fractures)

 

 

48

Q image thumb

MDx: Intramuscular hemorrhage

cause: trauma( esp penetrating wounds, fractures)

49

Is hemorrage a common lesion in muscle?

NO! If it is there, you should be thinking TRAUMA!

50

Your next consult is a rabbit...

Or a pig...

Or a puppy, take your pick...

Since birth cannot stand, limbs abducted, flattened chest, alert and otherwise normal.

Q image thumb

Morph Dx – Myocyte hypoplasia
Disease Dx - “Splay Leg” or “Swimmer Syndrome"

51

What is morphologically abnormal?

What pathological processes could account for this appearance?

How could this be caused?

Q image thumb

Myocytes are smaller in diameter

What pathological processes could account for this appearance?

Degeneration/Necrosis

Inflammation & Repair

Circulatory Disorders

Disorders of Growth

Deposits & Pigmentations

Pathology report:
Morph Dx – Myocyte hypoplasia
Disease Dx - “Splay Leg” or “Swimmer Syndrome"

Pathogenesis unknown currently

Genetic predisposition

Primary spinal /

neuromuscular disease?

Underlying infections?

Overfeeding?

Slippery flooring involved?

 

You give support to the limbs, and the mycocytes will catch up over time

52

Does myocyte hyperplasia occur?

 

Can myocytes proliferate??

Myocytes CAN NOT PROLIFERATE!!! because they are terminately proliferated

 

 

muscle hypertrophy i.e. going to the gym

A image thumb
53

Causes of myocyte hypertrophy

Causes of myocyte hypertrophy

• Exercise conditioning

• Compensatory

- decreased number/size functional myocytes, increased load on remaining

54

Causes of myocyte hyperplasia

Causes of myocyte hyperplasia “Double muscling”
• Inactivation of the regulatory gene myostatin (involved in myoblast cell progression to muscle fibers)

GENETIC

A image thumb
55

What is morphologically abnormal with this horse?

Gross morphological diagnosis?

Q image thumb

Muscles are lop-sided

Regional atrophy- gross morphological dx

Causes:

• Physiologic (Dis-use, aging)

• Cachexia/malnutrition

Endocrine disease – myocytes have surface receptors for hormones (hypoT, hyperA)

Denervation – myocyte maintenance requires trophic factors generated at neuromuscular junction; occurs quickly!

56

What is morphologically abnormal? ( from the horse case)

Q image thumb

The muscles from the atrophical horses would likely look like the one of the right.

Fibrosis and fatty infiltration (steatosis) often develop in long- standing atrophy

Notice that we can use the terms ‘atrophy’ and ‘hypertrophy’ when referring to muscle as a whole or to the diameter of a myocyte

57

What is abnormal?

Q image thumb

Larynx from a horse clinically diagnosed with laryngeal paralysis. Note L cricoarytenoideus dorsalis muscle (due to damage to the L recurrent laryngeal nerve).

58

Which cell type do neoplasms with striated muscle differentiation (‘rhabdomyoma/sarcoma’) derive from?

Pluripotential stem cells

(remember skeletal myocytes can NOT replicate even to form a neoplasm)

59

Q image thumb

 rear leg from a dog - rhabdomyosarcoma

very malignant

A image thumb
60

Q image thumb

Myoblast differentiation MDx: rhabdomyosarcoma

61

What do you have to use to tell if you have a rhabdomyosarcoma?

Immunohistochemistry for desmin

62

Q image thumb

 Rear leg from a dog - hemangiosarcoma from skeletal muscle

63

“Rufus”, 1 year old male Golden Retriever.....

Clinical signs

Exercise intolerant

Progressive generalized muscle weakness, atrophy

Joint contractures and angular deformities

Excessive drooling, problems eating- problems with muscles of mastication

What can we do to figure out what the pathological process was that resulted in these signs??

BIOPSY!

64

Rufus's histo

 

and what would cause this?

Q image thumb

Pathology report:
Morph Dx – Polyphasic myocyte degeneration and necrosis, chronic, with hypertrophy, atrophy, and fibrosis

Causes of polyphasic lesions:

Ongoing insults

Nutritional deficiency – vitamin E/Se

Ongoing toxicities

Genetic defects in myocyte structural/metabolic elements

Important point: Usually not possible to discern the cause of muscle injury with histopathology – supplemental tests, clinical history usually required!

65

What did Rufus have?

“Rufus”, 1 year old male Golden Retriever.....

Follow up

You research genetic myopathies of dogs and find “Muscular Dystrophy”

–  X-linked inherited myopathy reported in dogs and cats, especially G Retrievers

 Defects in dystrophin gene – cytoskeletal protein

You discuss with pathologist

Dystrophin tested on a fresh muscle sample is very low

You inform owner poor prognosis, no treatment

66

Which 3 pigments and tissue deposits are observed in skeletal muscle?

Lipofuscin- because myocytes are so long lived

Dystrophic calcification- because there is so much Ca+ in the ER

Exogenous pigments- ESPECIALLY from injections

67

Q image thumb

MDx: polyphasic myocyte degeneration and necrosis (with dystrophic calcification)

Disease: White muscle disease; cause – vit E/Se deficiency

Note calcification of myofibers secondary to degeneration/necrosis.

68

What’s up with these diaphragms of 600 sheep?

yellow plaques are going into the muscle

Q image thumb

EXOGENOUS DEPOSITS

Ba, Se, Au were on the spec

this is a suplement for Se that was given IP instead of SQ

A image thumb
69

Called in to investigate several deaths of ducks at a local pond. Some surviving are very weak.

What can we do to figure out what the pathological process was that resulted in these signs??

Pathology report:
Morph Dx – Open.
No lesions identified in over 20 sections examined. – nothing wrong with muscle or nervous system.

Botulism

 

cows chew on bones and get botulism

70

Botulism

Botulism

Pathogenesis:

Decaying organic matter-->Clostridium botulinum thrives and elaborates exotoxin into envir.->>>ingested -------> toxin inhibits Ach release from nerve terminals at neuromuscular junction ------>progressive generalized paralysis with death by cardiorespiratory failure

71

Other “biochemical” pathological processes resulting in severe muscular clinical signs:

Neuromuscular junction disorders – Botulism, myasthenia gravis, tick paralysis

Electrolyte derangements – hypokalemia (cats), hypocalcemia (cattle)

Misc inherited disorders of muscle metabolism –myotonias (often involve ion channel defects – inability of fibers to relax)