Difference between revisions of "Muscles Inflammatory - Pathology"

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==Myositis==
 +
 +
*Inflammation of muscle
 +
 +
 +
===Bacterial myositis===
 +
 +
*Bacteria gain entry via:
 +
**Direct penetration
 +
**Blood stream
 +
**Extension
 +
*Lesions caused:
 +
**Suppurative
 +
**Serosanguinous
 +
**Granulomatous
 +
 +
 +
====Abscesses====
 +
 +
*Caused by pyogenic bacteria
 +
*Usually:
 +
**[[Arcanobacter pyogenes|''Arcanobacterium pyogenes'']] in sheep and cattle
 +
**[[Respiratory Bacterial Infections - Pathology#Strangles|''Streptococcus equi'']] in horses
 +
**[[Corynebacterium species|''Corynebacterium pseudotuberculosis'']] in sheep and goats
 +
**[[Pasteurella species and Mannheimia haemolytica|''Pasteurella multocida'']] causes cellulitis in cats
 +
*Usually localised suppuration and necrosis of myofibres
 +
*Occasionally my spread via the fascia
 +
 +
 +
====Black leg====
 +
[[Image:Black leg myositis.jpg|right|thumb|100px|<small><center>Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 +
*Causative agent: [[Clostridium species|''Clostridium chauvoei'']]
 +
*May affect the fattest cattle at pasture in the summer
 +
*Rapid toxaemia -> death
 +
*If clinical signs observed:
 +
**Toxaemia -> pyrexia, depression, [[Lungs Circulatory - Pathology#Pulmonary oedema|pulmonary oedema]], circulatory collapse
 +
**Muscle lesions -> lameness, swollen hot muscles later becoming cool as necrosis sets in
 +
*Pathogenesis:
 +
**Spores gain entry to GI tract -> blood -> muscle -> lie latent
 +
**Under right conditions (usually anaerobic following injury) they germinate and bacilli grow
 +
**Toxin damages capillaries -> serosanguinous exudate
 +
**Muscle necrosis due to gas producing bacteria -> emphysaema and crepitus
 +
*Grossly:
 +
**Early stages
 +
***At muscle periphery
 +
***Dark red
 +
***Distended by serous or serosanguinous exudate
 +
***Wet cut surface
 +
**Old stages
 +
***Centre of lesion is full of gas bubbles, porous, dry, reddish black
 +
***Rancid odour
 +
*Histologically:
 +
**Early stages
 +
***Separation of myofibres by exudate
 +
***[[General Pathology - Necrosis#Coagulation Necrosis|Coagulative necrosis]]
 +
***No nuclei
 +
**Old stage
 +
***Fragmented muscle fibres separated by gas bubbles
 +
***Gram positive bacilli may be found in clumps
 +
 +
 +
====[[General Pathology - Necrosis#Gas Gangrene|Gas gangrene]]====
 +
 +
*Causative agents: [[Clostridium species|''Clostridium septicum, C. novyi, C. perfringens, C. sordelli'']]
 +
*Normally in soil
 +
*Bacteria gain entry as spores via penetrating wounds
 +
*Serohaemorrhagic myositis
 +
*If only subcutis and fascia are involved - '''malignant oedema'''
 +
*Toxaemia and septicaemia -> rapid death
 +
 +
 +
====[[Oral Cavity - Tongue#Actinobacillosis|Wooden tongue]]====
 +
 +
*Also called '''Actinobacillosis'''
 +
*Caused by [[Actinobacillus species|''Actinobacillus lignieresii'']]
 +
*Usually due to direct penetration into [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]] of cattle
 +
*Small granulomatous lesions containing 'sulfa granules' of large numbers of gram-negative rods
 +
 +
====Tuberculosis====
 +
 +
*Caused by [[Mycobacteria spp.|''Mycobacterium bovis'']]
 +
*Grossly:
 +
**Yellowish spherical nodules
 +
**[[General Pathology - Necrosis#Caseation Necrosis|Caseous content]]
 +
**Fibrous capsule usually
 +
*Histologically:
 +
**Granuloma
 +
**Central necrosis
 +
**Epitheliod and giant cells at periphery
 +
 +
 +
====[[Actinomycetes|''Actinomycosis bovis'']]====
 +
 +
*May extend to muscles, especially masseters, from [[Bones Inflammatory - Pathology#Osteomyelitis|osteomyelitis]]
 +
*Histologically:
 +
**Caseous or suppurative centres of lesions
 +
**Epithelioid and giant cells at periphery
 +
**'Sulfa granules' at centre - gram-positive branching rods
 +
 +
 +
====Botryomycosis====
 +
 +
*Caused by [[Staphylococcus spp.|''Staphylococcus aureus'']]
 +
*Occurs in horses and pigs usually due to wounds
 +
*Lowgrade persistent infection -> granulomatous lesions
 +
*Grossly:
 +
**Hard nodules with fibrous capsule in muscles
 +
**Contain yellow-brown pus and granules
 +
*Histologically:
 +
**Encapsulated granulomatous lesions
 +
**Central club colonies
 +
**Staphylococci are present
 +
 +
 +
===Viral myositis===
 +
 +
*Rare in the UK
 +
 +
====Porcine encephalomyelitis====
 +
 +
*Caused by [[Coronaviridae|Coronavirus]]
 +
*May cause multifocal myofibre necrosis + focal interstitial and perivascular lymphocyte, macrophage and neutrophil infiltration
 +
 +
 +
====Foot and Mouth disease====
 +
 +
*Caused by [[Picornaviridae|Apthovirus]]
 +
*Main presentation are vesicles
 +
*May also involve skeletal and heart muscle
 +
*Grossly:
 +
**Yellow streaks and grey foci
 +
*Histologically:
 +
**Segmental myofibre [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
**Infiltration of lymphocytes and neutrophils
 +
 +
 +
====Bluetongue====
 +
 +
*Caused by [[Reoviridae|bluetongue virus of family Reoviridae]]
 +
*Non-contagious
 +
*Insect-borne
 +
*Causes vasculitis, especially in oral cavity
 +
*Grossly:
 +
**Infarctions -> necrosis
 +
**Haemorrhage
 +
*Histologically:
 +
**Necrosis -> calcification or regeneration (depends on age of lesion)
 +
 +
 +
===Parasitic myositis===
 +
[[Image:taenia ovis cysticerci.jpg|right|thumb|100px|<small><center>''T. ovis'' cysticerci (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
[[Image:Sarcocyst in muscle.jpg|right|thumb|100px|<small><center>Sarcocyst (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
*Rare in domestic animals
 +
 +
 +
====Nematodes====
 +
 +
*[[Trichinelloidea|'''''Trichinella''''']] larvae
 +
**Particularly in pigs and dogs
 +
**Public health and economic importance
 +
**''T. spiralis'' affecting dogs, pigs, cats and humans is most common in hotter climates
 +
**Larvae distend myofibres
 +
**May be seen grossly if dead and calcified
 +
**Predilection for active muscles, ''e.g.'' diaphragm, intercostal, masseter and tongue muscles
 +
**Histologically:
 +
***Focal myositis - neutrophils, lymphocytes, eosinophils
 +
 +
*[[Ancylostomatoidea|''Ancylostoma'']] larvae
 +
**Cause inflammation and [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
*[[Ascaridoidea|Ascarid]] larvae
 +
*[[Dirofilaria immitis|''Dirofilaria immitis'']] in dogs causing ischaemic myopathy due to [[Muscles Degenerative - Pathology#Ischaemia|infartcs]]
 +
 +
 +
====Cestodes====
 +
 +
*[[Taenia|''Taenia solium, '']] - cysticercosis in swine and humans
 +
*[[Taenia|''T. ovis'']] - cysticercosis in sheep
 +
*[[Taenia|''T. saginata'']] in cattle cysticercosis
 +
*[[Taenia|''Multiceps serialis'']] in rabbits, primates coenurosis
 +
*[[Echinococcus|''Echinococcus granulosus'']] hydatid disease in herbivores and humans
 +
 +
====Protozoa====
 +
 +
*[[Tissue cyst-forming coccidia|'''''Toxoplasma gondii''''']]
 +
**Cats as final hosts
 +
**Intermediate hosts, birds and mammals have tachyzoites throughout body, infrequently in skeletal muscle
 +
**Histologically:
 +
***Multifocal [[Muscles Degenerative - Pathology#Necrosis|necrosis]] of myofibres
 +
***Lymphocyte and plasma cell infiltration
 +
***In later stages bradyzoite cysts
 +
*[[Tissue cyst-forming coccidia|'''''Neospora caninum''''']]
 +
**Necrotising inflammation of muscles
 +
**Myositis more severe than in toxoplasmosis
 +
*[[Tissue cyst-forming coccidia|'''''Sarcocystis''''']]
 +
**Histologically:
 +
***Merozoites causing focal and segmental [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
***May involve [[Muscles Degenerative - Pathology#Calcification|mineralisation]]
 +
***Non-purulent myositis with plasma cells, lymphocytes and macrophages
 +
**Diaphragm and masseters most severely affected
 +
*[[Bones Hyperplastic and Neoplastic - Pathology#Hepatozoon|'''''Hepatozoon americanum''''']]
 +
**Develop cysts in skeletal muscle of dogs and cats
 +
**May be accompanied by pyogranulomatous myositis - macrophages and neutrophils mainly with occasional other cells
 +
*'''''Trypanosoma'''''
 +
**Infrequent muscle lesions with mononuclear infiltrates
 +
**Dogs, cats and pigs are affected
 +
**Parasites lie between myofilaments
 +
**May cause fibre degeneration
 +
*'''''Babesia bovis'''''
 +
**In cattle
 +
**Infrequent muscle [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
 +
 +
====Arthropods====
 +
 +
*Dipterious larvae causing myiasis
 +
*[[Insecta|''Hypoderma'' spp.]] in cattle
 +
**May occasionally burrow into muscle
 +
 +
 +
===Immune-mediated myositis===
 +
 +
====Masticatory muscle myositis (MMM)====
 +
 +
*Occurs in dogs
 +
*Tends to affect the masseter and temporalis muscles
 +
*Autoantibodies selectively attack muscles of mastication (type IIM fibres)
 +
*Acute stage = eosinophilic myositis
 +
**Extremely swollen, painful, hard masticatory muscles
 +
*Chronic stage = atrophic myositis
 +
**Atrophy may occur without previous acute stage
 +
*Grossly:
 +
**Bilateral but not necessarily symmetrical
 +
**At first, enlarged and oedematous muscles becominf dark red, firm with reddish streaks and yellowiss foci
 +
*Histologically:
 +
**Acute lesions:
 +
***Mainly eosinophilic infiltrate, few lymphocytes, monocytes and plasma cells
 +
***In recurrent disease plasma cells predominate
 +
***[[Muscles Degenerative - Pathology#Necrosis|Necrotic]] myofibres, [[Muscles Degenerative - Pathology#Atrophy|atrophy]] and attempted [[Muscles - normal#Regeneration|regeneration]]
 +
**Chronic stage:
 +
***[[Muscles Degenerative - Pathology#Atrophy|Atrophy]] predominates
 +
***Fasciculi are shrunken
 +
***Condensation of stroma -> enlarged endomysium
 +
***Focal plasma cell and lymphocyte infiltration
 +
 +
 +
====[[Muscles Developmental - Pathology#Canine dermatomyositis|Canine dermatomyositis]]====
 +
 +
 +
===Idiopathic myositis===
 +
 +
====Canine polymyositis====
 +
 +
*DOES NOT include MMM above
 +
*Rare
 +
*Clinical signs:
 +
**Muscle pain
 +
**Fever
 +
**Weakness, particularly in hind limbs
 +
*Grossly:
 +
**Inflammation is accompanied by muscle necrosis and regeneration
 +
*Histologically:
 +
**Inflammatory foci with lymphocytes, plasma cells and occasionally eosinophils
 +
*Possibly immunological cause
 +
*Single biopsy may not be enough to make the diagnosis as it tends to be multifocal and disseminated
 +
*Lesions similar to some infectious causes (such as [[Tissue cyst-forming coccidia|''Toxoplasma gondii'']])
 +
 +
 +
====Canine bilateral extraocular polymyositis====
 +
 +
*In Golden retrievers
 +
*Very rare
 +
*Clinical signs:
 +
**Acute bilateral exophthalmos
 +
*Involves only extraocular muscles except for retractor blbi
 +
*Grossly:
 +
**Swollen and pale extraocular muscles
 +
*Histologically:
 +
**Sterile myositis
 +
**Multifocal necrosis of myofibres
 +
**Lymphocytic, histiocytic and plasmacytic infiltrate with few neutrophils
 +
 +
 +
====Bovine and ovine eosinophilic myositis====
 +
 +
*Unknown aetiology
 +
*Major cell involved is eosinphil
 +
*Usually noticed at slaughter - green muscle discoloration
 +
*May be caused by degenteration of [[Tissue cyst-forming coccidia|''Sarcocystis'' spp.]]
 +
*Grossly:
 +
**Green discolored areas, well demarcated
 +
**Mostly in muscles of back and thighs
 +
*Histologically:
 +
**Massive eosinophil infiltration
 +
**Muscle fibres may degenerate
 +
**In old lesions - endimysial fibrosis, myofibre atrophy, some regeneration, lymphocytes, plasma cells, macrophages and few eosinophils
 +
**Capsule may form

Revision as of 20:15, 18 August 2008

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()Map MUSCULOSKELETAL SYSTEM (Map)
MUSCLES



Myositis

  • Inflammation of muscle


Bacterial myositis

  • Bacteria gain entry via:
    • Direct penetration
    • Blood stream
    • Extension
  • Lesions caused:
    • Suppurative
    • Serosanguinous
    • Granulomatous


Abscesses


Black leg

Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)
  • Causative agent: Clostridium chauvoei
  • May affect the fattest cattle at pasture in the summer
  • Rapid toxaemia -> death
  • If clinical signs observed:
    • Toxaemia -> pyrexia, depression, pulmonary oedema, circulatory collapse
    • Muscle lesions -> lameness, swollen hot muscles later becoming cool as necrosis sets in
  • Pathogenesis:
    • Spores gain entry to GI tract -> blood -> muscle -> lie latent
    • Under right conditions (usually anaerobic following injury) they germinate and bacilli grow
    • Toxin damages capillaries -> serosanguinous exudate
    • Muscle necrosis due to gas producing bacteria -> emphysaema and crepitus
  • Grossly:
    • Early stages
      • At muscle periphery
      • Dark red
      • Distended by serous or serosanguinous exudate
      • Wet cut surface
    • Old stages
      • Centre of lesion is full of gas bubbles, porous, dry, reddish black
      • Rancid odour
  • Histologically:
    • Early stages
    • Old stage
      • Fragmented muscle fibres separated by gas bubbles
      • Gram positive bacilli may be found in clumps


Gas gangrene


Wooden tongue

  • Also called Actinobacillosis
  • Caused by Actinobacillus lignieresii
  • Usually due to direct penetration into tongue of cattle
  • Small granulomatous lesions containing 'sulfa granules' of large numbers of gram-negative rods

Tuberculosis

  • Caused by Mycobacterium bovis
  • Grossly:
  • Histologically:
    • Granuloma
    • Central necrosis
    • Epitheliod and giant cells at periphery


Actinomycosis bovis

  • May extend to muscles, especially masseters, from osteomyelitis
  • Histologically:
    • Caseous or suppurative centres of lesions
    • Epithelioid and giant cells at periphery
    • 'Sulfa granules' at centre - gram-positive branching rods


Botryomycosis

  • Caused by Staphylococcus aureus
  • Occurs in horses and pigs usually due to wounds
  • Lowgrade persistent infection -> granulomatous lesions
  • Grossly:
    • Hard nodules with fibrous capsule in muscles
    • Contain yellow-brown pus and granules
  • Histologically:
    • Encapsulated granulomatous lesions
    • Central club colonies
    • Staphylococci are present


Viral myositis

  • Rare in the UK

Porcine encephalomyelitis

  • Caused by Coronavirus
  • May cause multifocal myofibre necrosis + focal interstitial and perivascular lymphocyte, macrophage and neutrophil infiltration


Foot and Mouth disease

  • Caused by Apthovirus
  • Main presentation are vesicles
  • May also involve skeletal and heart muscle
  • Grossly:
    • Yellow streaks and grey foci
  • Histologically:
    • Segmental myofibre necrosis
    • Infiltration of lymphocytes and neutrophils


Bluetongue

  • Caused by bluetongue virus of family Reoviridae
  • Non-contagious
  • Insect-borne
  • Causes vasculitis, especially in oral cavity
  • Grossly:
    • Infarctions -> necrosis
    • Haemorrhage
  • Histologically:
    • Necrosis -> calcification or regeneration (depends on age of lesion)


Parasitic myositis

T. ovis cysticerci (Image sourced from Bristol Biomed Image Archive with permission)
Sarcocyst (Image sourced from Bristol Biomed Image Archive with permission)
  • Rare in domestic animals


Nematodes

  • Trichinella larvae
    • Particularly in pigs and dogs
    • Public health and economic importance
    • T. spiralis affecting dogs, pigs, cats and humans is most common in hotter climates
    • Larvae distend myofibres
    • May be seen grossly if dead and calcified
    • Predilection for active muscles, e.g. diaphragm, intercostal, masseter and tongue muscles
    • Histologically:
      • Focal myositis - neutrophils, lymphocytes, eosinophils


Cestodes

Protozoa

  • Toxoplasma gondii
    • Cats as final hosts
    • Intermediate hosts, birds and mammals have tachyzoites throughout body, infrequently in skeletal muscle
    • Histologically:
      • Multifocal necrosis of myofibres
      • Lymphocyte and plasma cell infiltration
      • In later stages bradyzoite cysts
  • Neospora caninum
    • Necrotising inflammation of muscles
    • Myositis more severe than in toxoplasmosis
  • Sarcocystis
    • Histologically:
      • Merozoites causing focal and segmental necrosis
      • May involve mineralisation
      • Non-purulent myositis with plasma cells, lymphocytes and macrophages
    • Diaphragm and masseters most severely affected
  • Hepatozoon americanum
    • Develop cysts in skeletal muscle of dogs and cats
    • May be accompanied by pyogranulomatous myositis - macrophages and neutrophils mainly with occasional other cells
  • Trypanosoma
    • Infrequent muscle lesions with mononuclear infiltrates
    • Dogs, cats and pigs are affected
    • Parasites lie between myofilaments
    • May cause fibre degeneration
  • Babesia bovis


Arthropods

  • Dipterious larvae causing myiasis
  • Hypoderma spp. in cattle
    • May occasionally burrow into muscle


Immune-mediated myositis

Masticatory muscle myositis (MMM)

  • Occurs in dogs
  • Tends to affect the masseter and temporalis muscles
  • Autoantibodies selectively attack muscles of mastication (type IIM fibres)
  • Acute stage = eosinophilic myositis
    • Extremely swollen, painful, hard masticatory muscles
  • Chronic stage = atrophic myositis
    • Atrophy may occur without previous acute stage
  • Grossly:
    • Bilateral but not necessarily symmetrical
    • At first, enlarged and oedematous muscles becominf dark red, firm with reddish streaks and yellowiss foci
  • Histologically:
    • Acute lesions:
      • Mainly eosinophilic infiltrate, few lymphocytes, monocytes and plasma cells
      • In recurrent disease plasma cells predominate
      • Necrotic myofibres, atrophy and attempted regeneration
    • Chronic stage:
      • Atrophy predominates
      • Fasciculi are shrunken
      • Condensation of stroma -> enlarged endomysium
      • Focal plasma cell and lymphocyte infiltration


Canine dermatomyositis

Idiopathic myositis

Canine polymyositis

  • DOES NOT include MMM above
  • Rare
  • Clinical signs:
    • Muscle pain
    • Fever
    • Weakness, particularly in hind limbs
  • Grossly:
    • Inflammation is accompanied by muscle necrosis and regeneration
  • Histologically:
    • Inflammatory foci with lymphocytes, plasma cells and occasionally eosinophils
  • Possibly immunological cause
  • Single biopsy may not be enough to make the diagnosis as it tends to be multifocal and disseminated
  • Lesions similar to some infectious causes (such as Toxoplasma gondii)


Canine bilateral extraocular polymyositis

  • In Golden retrievers
  • Very rare
  • Clinical signs:
    • Acute bilateral exophthalmos
  • Involves only extraocular muscles except for retractor blbi
  • Grossly:
    • Swollen and pale extraocular muscles
  • Histologically:
    • Sterile myositis
    • Multifocal necrosis of myofibres
    • Lymphocytic, histiocytic and plasmacytic infiltrate with few neutrophils


Bovine and ovine eosinophilic myositis

  • Unknown aetiology
  • Major cell involved is eosinphil
  • Usually noticed at slaughter - green muscle discoloration
  • May be caused by degenteration of Sarcocystis spp.
  • Grossly:
    • Green discolored areas, well demarcated
    • Mostly in muscles of back and thighs
  • Histologically:
    • Massive eosinophil infiltration
    • Muscle fibres may degenerate
    • In old lesions - endimysial fibrosis, myofibre atrophy, some regeneration, lymphocytes, plasma cells, macrophages and few eosinophils
    • Capsule may form
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