Difference between revisions of "Muscles Inflammatory - Pathology"

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#redirect[[:Category:Muscles - Inflammatory Pathology]]
 
 
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|backcolour =CDE472
 
|linkpage =Musculoskeletal System - Pathology
 
|linktext =Musculoskeletal System
 
|maplink = Musculoskeletal System (Content Map) - Pathology
 
|pagetype =Pathology
 
|sublink1=Muscles - Pathology
 
|subtext1=MUSCLES
 
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<br>
 
==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
 
***[[Necrosis - Pathology#Coagulation Necrosis|Coagulative necrosis]]
 
***No nuclei
 
**Old stage
 
***Fragmented muscle fibres separated by gas bubbles
 
***Gram positive bacilli may be found in clumps
 
 
 
 
 
====[[Necrosis - Pathology#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
 
 
 
 
 
====[[Tongue - Pathology#Actinobacillosis|Wooden tongue]]====
 
 
 
*Also called '''Actinobacillosis'''
 
*Caused by [[Actinobacillus species|''Actinobacillus lignieresii'']]
 
*Usually due to direct penetration into [[Tongue - Pathology - 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
 
**[[Necrosis - Pathology#Caseation Necrosis|Caseous content]]
 
**Fibrous capsule usually
 
*Histologically:
 
**Granuloma
 
**Central necrosis
 
**Epitheliod and giant cells at periphery
 
 
 
 
 
====[[Actinomycetes|''Actinomycosis bovis'']]====
 
*"Lumpy jaw"
 
*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 - WikiBlood|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 - WikiBlood|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====
 
 
 
*[[Toxoplasma|'''''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
 
*[[Neospora|'''''Neospora caninum''''']]
 
**Necrotising inflammation of muscles
 
**Myositis more severe than in toxoplasmosis
 
*[[Sarcocystis|'''''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 - WikiBlood|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 - WikiBlood|monocytes]]]] and plasma cells
 
***In recurrent disease plasma cells predominate
 
***[[Muscles Degenerative - Pathology#Necrosis|Necrotic]] myofibres, [[Muscles Degenerative - Pathology#Atrophy|atrophy]] and attempted [[Muscle Regeneration - Anatomy & Physiology|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 [[Toxiplasma|''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 - WikiBlood|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|''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
 

Latest revision as of 23:15, 5 March 2011