The pathologic features of vasculitic neuropathy are evident:

• Zonal involvement of the nerve fascicles with:
  • Loss of myelin.
  • Wallerian degeneration.
  • Regeneration.

Chronic active vasculitis:

• Active features:
  • Perivascular and mural inflammatory infiltrate including lymphocytes and histiocytes.
  • Plump (reactive) endothelial cells.
  • Vessel wall cell death (necrosis).
• Chronic features:
  • Vessel wall thickening due to hyperplasia.
  • Dense fibrous tissue around the vessel.

The vasculitis in this case affects both small (< 100 micrometers) and medium vessels. Granulomas are absent. Eosinophils are rare. Histomorphologic, diagnostic considerations are polyarteritis nodosa and microscopic polyangiitis.

• 
  Low mag.
• 
  Intermed. mag.
• 
  High mag.

• 
  Intermed. mag.
• 
  High mag.
• 
  Very high mag.