Difference between revisions of "Masticatory Muscle Myositis"

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(MMM)
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==Overview==
*Occurs in dogs
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Masticatory muscle myositis (MMM) occurs in dogs and tends to affect the [[Mastication#Jaw Closing Muscles|masseter]] and [[Cheeks|temporalis]] muscles. Autoantibodies selectively attack the muscle of mastication, which contain type IIM fibres. MMM can be classified as either acute or chronic:
*Tends to affect the masseter and temporalis muscles
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*'''Acute stage''': Eosinophilic myositis with extremely swollen, painful, hard masticatory muscles.
*Autoantibodies selectively attack muscles of mastication (type IIM fibres)
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*'''Chronic stage''': Atrophic myositis where atrophy may occur without previous acute stage.
*Acute stage = eosinophilic myositis
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**Extremely swollen, painful, hard masticatory muscles
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Grossly MMM is normally bilateral, but not necessarily symmetrical.
*Chronic stage = atrophic myositis
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**Atrophy may occur without previous acute stage
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==Histology==
*Grossly:
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**Bilateral but not necessarily symmetrical
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'''Acute lesions''':  
*Histologically:
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*Mainly eosinophilic infiltrate, few lymphocytes, [[Monocytes|monocytes]] and plasma cells.
**Acute lesions:
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*In recurrent disease plasma cells predominate.
***Mainly eosinophilic infiltrate, few lymphocytes, [[Monocytes|monocytes]] and plasma cells
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*[[Muscle Necrosis|Necrotic]] myofibres, [[Muscle Atrophy|atrophy]] and attempted [[Muscle Regeneration|regeneration]].
***In recurrent disease plasma cells predominate
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***[[Muscle Necrosis|Necrotic]] myofibres, [[Muscle Atrophy|atrophy]] and attempted [[Muscle Regeneration|regeneration]]
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'''Chronic lesions''':
**Chronic stage:
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*[[Muscle Atrophy|Atrophy]] predominates.
***[[Muscle Atrophy|Atrophy]] predominates
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*Fasciculi are shrunken.
***Fasciculi are shrunken
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*Condensation of stroma leading to an enlarged endomysium.
***Condensation of stroma -> enlarged endomysium
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*Focal plasma cell and lymphocyte infiltration.
***Focal plasma cell and lymphocyte infiltration
 
  
  
 
[[Category:Immune-Mediated Myositis]]
 
[[Category:Immune-Mediated Myositis]]
 
[[Category:To Do - Musculoskeletal]]
 
[[Category:To Do - Musculoskeletal]]
[[Category:LisaM reviewing]]
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[[Category:Other Oral Conditions]]
[[category:To Do - Dentistry preMars]] <!-----G, please make it look nicer, ta.---------->
 

Latest revision as of 16:15, 28 October 2014

Overview

Masticatory muscle myositis (MMM) occurs in dogs and tends to affect the masseter and temporalis muscles. Autoantibodies selectively attack the muscle of mastication, which contain type IIM fibres. MMM can be classified as either acute or chronic:

  • Acute stage: Eosinophilic myositis with extremely swollen, painful, hard masticatory muscles.
  • Chronic stage: Atrophic myositis where atrophy may occur without previous acute stage.

Grossly MMM is normally bilateral, but not necessarily symmetrical.

Histology

Acute lesions:

Chronic lesions:

  • Atrophy predominates.
  • Fasciculi are shrunken.
  • Condensation of stroma leading to an enlarged endomysium.
  • Focal plasma cell and lymphocyte infiltration.