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Immune Myopathies: MDA5 antibody-associated

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Myopathologic features ^1,2

Perimysium
  Macrophages: Scattered perimysial & endomysial; Some perivascular
Muscle fibers
  Necrosis & Regeneration: Few fibers; Scattered
  MHC Class I: Upregulated in some patients
  LC3 aggregates
  NOS2, HSP70, NCAM in sarcoplasm, especially in perifascicular fibers near inflammation
  Interferon-related molecules: RIG-I; ISG15
Capillaries
  Normal or Mildly reduced numbers

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H&E stain

Fiber size: Varied
Necrosis & Regeneration: Scattered

H&E stain

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Gomori trichrome stain

Aggregates: Central; Irregular shapes

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Acid phosphatase stain

Necrosis & Regeneration: Cells
  Scattered in endomysium
  Replacing necrotic muscle fibers

Esterase stain

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ATPase pH 4.3 stain

Type 2 muscle fiber predominance

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NADH stain

Internal architecture: Linearized in type 2 muscle fibers

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LC3 stain

Aggregates: Punctate; Clustered

LC3 stain

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MHC Class I stain

MHC Class I: Upregulated on all muscle fibers

MHC Class I stain

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Ulex stain

Capillaries: Corkscrew shape

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Return to Inflammatory myopathies
Return to IMPP
Return to Pathology index
Return to MDA5


References
1. Curr Opin Rheumatol 2011;23:595-604
2. Am J Pathol 2016;186:691-700

9/24/2019