Immune Myopathies: MDA5 antibody-associated

Myopathologic features 1,2

  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
  Normal or Mildly reduced numbers

H&E stain
Fiber size: Varied
Necrosis & Regeneration: Scattered

H&E stain

Gomori trichrome stain
Aggregates: Central; Irregular shapes

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

Esterase stain

ATPase pH 4.3 stain
Type 2 muscle fiber predominance

NADH stain
Internal architecture: Linearized in type 2 muscle fibers

LC3 stain
Aggregates: Punctate; Clustered

LC3 stain

MHC Class I stain
MHC Class I: Upregulated on all muscle fibers

MHC Class I stain

Ulex stain
Capillaries: Corkscrew shape

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Return to IMPP
Return to Pathology index
Return to MDA5

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