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''':  
**At first, enlarged and oedematous muscles becominf dark red, firm with reddish streaks and yellowiss foci
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*Mainly eosinophilic infiltrate, few lymphocytes, [[Monocytes|monocytes]] and plasma cells.
*Histologically:
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*In recurrent disease plasma cells predominate.
**Acute lesions:
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*[[Muscle Necrosis|Necrotic]] myofibres, [[Muscle Atrophy|atrophy]] and attempted [[Muscle Regeneration|regeneration]].
***Mainly eosinophilic infiltrate, few lymphocytes, [[Monocytes|monocytes]] and plasma cells
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***In recurrent disease plasma cells predominate
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'''Chronic lesions''':
***[[Muscle Necrosis|Necrotic]] myofibres, [[Muscle Atrophy|atrophy]] and attempted [[Muscle Regeneration|regeneration]]
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*[[Muscle Atrophy|Atrophy]] predominates.
**Chronic stage:
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*Fasciculi are shrunken.
***[[Muscle Atrophy|Atrophy]] predominates
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*Condensation of stroma leading to an enlarged endomysium.
***Fasciculi are shrunken
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*Focal plasma cell and lymphocyte infiltration.
***Condensation of stroma -> enlarged endomysium
 
***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]]

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.