Neuromuscular

Immune Myopathies: MDA5 antibody-associated


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


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

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

4/13/2017