Eosinophilic Vasculitis

Axon loss
Granuloma
Muscle & Myopathy
Subperineurial edema
Vasculitic pathology
Wallerian degeneration

H&E stain

Eosinophils in Vessel wall

Vasculitic Pathology

H&E stain

Vessels
Wall: Damaged; Cellular
Lumen: Lost
Epineurium
Eosinophils (Scattered) & other Cells
Nerve fascicle
Subpoerineurial edema

Congo red stain

VvG stain

Vessels
Wall: Damaged; Cellular; No fibrils
Endothelial cells: Large
Lumen: Lost

H&E stain

Vessels
Wall: Damaged; Cellular; No fibrils
Endothelial cells: Large
Lumen: Lost

VvG stain

VvG stain

Vessels: Three types
Within cell focus: No fibrils; Endothelial cells large
Vein: No fibrils
Vascular remnants: Clustered

Congo red stain

Inflammatory Cell Focus
Contains scattered eosinophils

Gomori trichrome stain

VvG stain

Granuloma: Epineurial
All cells in focus stain for acid phosphatase

Acid phosphatase stain

Acid phosphatase stain

Vasculopathy: Smaller Epineurial Vessels

VvG stain

Epineurial Vessels: Small
Surrounded by: Cells; Pale epineurial connective tissue

H&E stain

Epineurial Vessels: Neovascularization
Multiple small vessels within region of larger vessels

UEA I stain

Histiocytes in several structures
Epineurial Vessel: Acid phosphatase stained connective tissue inside fibril layer
Perineurium around small nerve fascicle (Arrow): Histiocytic cells
Epineurial connective tissue: Scattered histiocytic cells

Acid phosphatase stain

Fascicle Pathology: Subperineurial Edema

H&E stain

Subperineurial Edema
Pale-stained region under Perineurium

Gomori trichrome stain

Eosinophils: Within area of subperineurial edema

H&E stain

Wallerian Degeneration

VvG stain

Wallerian Degeneration: Early
Myelin sheath
Pale; Vesicular; Irregular (Arrow, Above)
Acid phosphatase stain (Below)
See: Intramuscular nerve

Acid phosphatase stain

Wallerian Degeneration: Intramuscular Nerve

VvG stain

VvG stain

Wallerian Degeneration: Early
Myelin sheath
Pale; Vesicular; Irregular (Arrow, Above)
Acid phosphatase stain (Below)

Acid phosphatase stain

Axon Loss
Differential: Intrafasciclar
More loss of large (Green) axons in some regions
NCAM-stained Schwann cells: Empty (Red) without associated axons
Active: Punctate or Irregular neurfilament staining

Neurofilament (Green) + NCAM (Red)

Axon Loss: Acute
Loss of large axons within pale areas (Myelin)
Punctate or Irregular neurofilament staining

Neurofilament stain

Axon Loss: Acute
Regions of myelin abnormally express NCAM

NCAM stain

Neurofilament (Green) + MBP (Red)

Axon Loss: Acute
Regions of myelin (MBP above or P0 below) have no axons

Neurofilament (Green) + P0 (Red)

Eosinophilic Vasculitis: Muscle features

Myopathy
Vasculitis

H&E stain

Histiocytic Vasculitis
Vessel location: Perimysium
Perivascular cells: Mostly histiocytes

H&E stain

Eosinophilic Vasculitis
Fibrinoid Necrosis: Inside fibril layer
Fibril layer: Irregular damaged
Surrounding vessel wall: Contains many histiocytes; Little other structure

VvG stain

Acid phosphatase stain

Histiocytic Vasculitis
Vessel location: Perimysium
Perivascular cells: Mostly histiocytes

Acid phosphatase stain

CD4 stain

Histiocytic Vasculitis
Vessel location: Perimysium
Perivascular cells: Often stain for CD4 & MxA; Few stain for CD8

MxA stain

CD8 stain

Eosinophilic Vasculitis: Myopathic features

H&E stain

Muscle Fibers
Sizes: Moderately varied
Internal nuclei: Some fibers

VvG stain

Acid phosphatase stain

Muscle Fibers: Internal Architecture
Cytoplasmic aggregates
Acid phosphatase positive (Above)
Contain LC3 (Autophagy marker; Below)

LC3 stain

MHC Class I stain

Muscle fibers
MHC1 upregulation
Perimysial vessels
Irregular fragments without lumens (Below; Arrow)

MHC Class I stain

C5b-9 deposition
Location: Connective tissue, Endomysial & Perimysial

C_5b-9 stain

CD163 stain

Histiocytic markers
CD163 histiocytes: Scattered in endomysium & perimysium (Above)
HAM56: Unusual distribution on endomysium & around surface of muscle fibers (Below)

HAM56 stain

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7/3/2023