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Enterovirus-associated Inflammatory Myopathy (EVIM)

EVIM   General pattern   Cells (Inflammation)   Connective tissue   Muscle fibers   Capillaries Also see   Dermatomyopathies   IMPP   Dermatomyositis: Adult, IMPP   Jo-1 muscle pathology

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EVIM: General Pattern

• Inflammation
  • Cell types: Lymphocytes & Histiocytes
  • Location: Vascular perimysium
• Connective tissue pathology
  • Inflammation: Perimysium & Epimysium
  • Structure: Mild damage
• Muscle fibers
  • MHC I up-regulation
  • COX- fibers
  • Morphologic damage: Minor
• Capillaries
  • Large
  • Numbers: Mild loss

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H&E stain

Perimysial cellularity

• Cell foci: Localized to vascular regions of perimysial connective tissue
• Muscle fibers: Mild, or no, involvement

H&E stain

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H&E stain

EVIM: Perimysial cells (Inflammation)

• Cells in perimysium are histiocytic (Above; Arrow). Features include
  • Large nuclei
  • Prominent cytoplasm
  • Staining for Acid Phosphatase, Esterase & CD-68

H&E stain

Cells
  Nuclei: Moderately large
  Cytoplasm: Moderate amount

H&E stain

CD3 stain

Cell phenotypes
  May stain for CD3, CD4, CD68, or CD8

CD4 stain

CD8 stain

Cell phenotypes
  CD8 lymphocytes in perimysium & scattered in endomysium

CD8 stain

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Acid phosphatase stain

Cell types
  Some are histocytic with Acid phosphatase & esterase staining

Esterase stain

Esterase stain

Cell types
  Some are histocytic with Esterase or CD68 staining

CD68 stain

Cell phenotypes
  Histiocytes stain for CD68

CD68 stain

Cell phenotypes
  Histiocytes in perimysium stain for CD68

CD68 stain

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Connective tissue

CD68 stain

Epimysium contains acid phosphatase & CD68+ histiocytes

Acid phosphatase stain

Connective tissue
  Stains for Acid phosphatase+ cells & Alkaline phosphatase

Alkaline phosphatase stain

Alkaline phosphatase stain

Connective tissue
Stains for alkaline phosphatase & C_5b-9

C5b-9 stain

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UEA-I stain

Connective tissue
  Unusual staining for UEA-I lectin (Usually endothelial stain)

UEA-I stain

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MHC Class I stain

MHC Class I
  Upregulated on muscle fibers
  Stains cells in perimysium

MHC Class I stain

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Perimysial connnective tisue structure
  May be mildly damaged

Gomori trichrome stain

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Muscle fibers: Pathology

MHC Class I stain

Muscle fibers
  MHCI: Diffusely up-regulated on muscle fibers

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ATPase ph 4.3 stain

Muscle fibers
  Increased numbers of immature, 2C fibers

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COX stain

Mitochondria
  Some fibers have reducved COX staining

COX stain

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VvG stain

Target-like structures
  Stain dark on VvG & LC3

LC3 stain

LC3 stain

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VvG stain

Muscle fiber internal architecture: May be irregular

NADH stain

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Endomysial Capillaries

UEA-I stain

Endomysial Capillaries
  Mildly large & dark-stained
  Numbers: Mildly reduced; a few muscle fibers have no adjacent capillary

UEA-I stain

UEA-I stain

Esterase stain

MxA stain

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EVIM: Endomysial cells, scattered

Congo red stain

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Return to Inflammatory myopathies
Return to IMPP

References
1. Curr Opin Rheumatol 2011;23:595-604

10/9/2020