Difference between revisions of "Muscles Inflammatory - Pathology"
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Revision as of 18:59, 3 March 2011
Myositis
Viral myositis
Parasitic Myositis
- Rare in domestic animals
Nematodes
- Trichinella larvae
- Ancylostoma larvae
- Cause inflammation and necrosis
- Ascarid larvae
- Dirofilaria immitis in dogs causing ischaemic myopathy due to infartcs
Cestodes
- Taenia solium, - cysticercosis in swine and humans
- T. ovis - cysticercosis in sheep
- T. saginata in cattle cysticercosis
- Multiceps serialis in rabbits, primates coenurosis
- Echinococcus granulosus hydatid disease in herbivores and humans
Protozoa
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
- Acute lesions:
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