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Dermatomyopathies with TIF1-γ (TRIM33) Antibodies

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• Pathology patterns: General
  • Dermatomyositis with Vascular Pathology (DM-VP)
  • Regional Ischemic Immune Myopathy (RIIM)
• Anatomic distribution: Regionally varied pathology
  • Myopathology: Most near vascular bundles in perimysium
  • Muscle fibers: Perifascicular myopathy & atrophy
  • Perimysium: Most inflammation in vascular perimysium
• Muscle fiber pathology: Regional
  • Vacuoles
  • Aggregates
  • Internal architecture: Irregular
  • COX stain: Reduced in regions (DM-VP syndromes)
  • Necrosis: Varied
    • Little or None: DM-VP syndromes
    • Regional: RIIM syndromes
  • Myonuclei: Enlarged
• Vessels
  • Capillaries (Endomysial)
    • C_5b-9 deposits: In regions of muscle fiber pathology
    • Ulex stain: Reduced numbers
    • Esterase stain: Increased
    • Alkaline phosphatase stain: Increased
  • Perivascular (Perimysial) inflammation: Some patients
• Perimysium
  • Inflammation: Mosly in vascular perimysium

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Muscle Fiber Pathology Distribution: Perifascicular Atrophy near Avascular Perimysium

H&E stain

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Muscle Fiber Pathology Distribution: Near or Around Perimysial vessels

ATPase pH 4.3 stain

Perivascular pathology (Arrows point to perimysial vascular bundle)
 Muscle fibers with abnormal internal architecture near Perimysial vessels

Cytochrome Oxidase stain

Cytochrome Oxidase stain

Perivascular pathology: Abnormal muscle fibers near Perimysial vessels with inflammation

ATPase pH 4.3 stain

Congo red stain

Perivascular pathology: Abnormal muscle fibers near Perimysial vessels

VvG stain

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Perivascular Pathology
  Abnormal (small) muscle fibers & capillary loss in region neighboring intermediate sized vessels

UEAI stain

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Perifascicular Atrophy, Mild

NADH stain

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Capillary Pathology

Esterase stain

Endomysial capillaries
  Stain abnormally for esterase

Esterase stain

Esterase stain

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Endomysial capillaries
  Mildly large

Gomori trichrome stain stain

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Alkaline phosphatase stain

Endomysial capillaries
  Increased numbers stain with alkaline phosphatase

Alkaline phosphatase stain

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Endomysial capillaries
  Staining for C_5b-9 in regions with muscle fiber pathology

C5b-9 stain

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UEA1 stain

Endomysial capillaries
  Reduced regional staining in TIF1-γ DM patient (Above)
  Normal adult: Every muscle fiber has at least one adjacent capillary (Below)

UEA1 stain

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UEA1 stain

TIF1-γ DM patient
  Reduced numbers of stained endomysial capillaries in region near perimysial vessel

UEA1 stain

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UEA1 stain

Normal adult: Every muscle fiber has at least one adjacent capillary

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Muscle Fiber Pathology: Vacuoles & Aggregates

H&E stain

H&E stain

Cytoplasmic Agregates & Vacuoles

H&E stain

VvG stain

Congo red stain

Cytoplasmic Agregates & Vacuoles

Congo red stain

ATPase pH 9.4 stain

Internal architecture: Irregular
  More abnormal in type 1 muscle fibers

NADH stain

NADH stain

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AMPDA trichrome stain

Cytoplasmic Agregates & Vacuoles
  One muscle fiber has cytoplassmic bodies (Below)

Gomori trichrome stain

SDH stain

SDH stain

Mitochondrial pathology
  SDH: Irregular internal architecture; Normal levels of staining
  COX: Irregular internal architecture; Variably reduced levels of staining

COX stain

Acid Phosphatase stain

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LC3 stain

LC3: Present in some muscle fiber aggregates
  Similar patterns may occur in DM-VP

LC3 stain

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MHC Class I: Upregulation by all muscle fibers

MHC Class I stain

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Perimysial Pathology

H&E stain

Vascular Perimysium: Cellularity

H&E stain

H&E stain

CD45 stain

Vascular Perimysium: Cellularity

CD8 stain

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5/1/2022