Small Vessel Pathology (Capillaries or Endoneurial Microvessels) 2

  Muscle: Normal
  Endoneurial Microvessels
Capillary pathology
    C5b-9 Deposits
    SRP Myopathy
    TS-HDS neuropathy
  Endoneurial inflammation
  Subperineurial edema
  Thickened vessel walls
Endomysial Capillary: Normal


Capillary: Normal
  Endothelial cell = E: Inside basal lamina
  Pericyte = P: Within basal lamina

Capillary Structure

Basement membrane
  Around & outside endothelial cell layer
  May be homogeneous or layered
  Contains pericytes (P)
    Collagen IV
    Glycoproteins: Fibronectin, Nidogen-1, Nidogen-2 (Entactin)
    Proteoglycans (as HSPG): Perlecan, Agrin
  Thickening: Differential diagnosis
Endothelial cells (E)
  Surround lumen
  Stain: Ulex Europaeus Aagglutinin I (UEAI)
Pericytes (P)
  Location: Within basal lamina of vessel wall
  Frequency vs Endothelial cells: 1:10 to 1:100
  Stain: PDGRFβ
Smooth muscle
  Stain: Smooth muscle actin

Endomysial Capillaries: Normal

UEA I stain
Endomysial capillaries: Normal
  Normal number: Every muscle fiber has at least one adjacent capillary
  Orientation: Run parallel to muscle fiber length; Cut in cross-section

UEA I stain
All muscle fibers have at least one adjacent capillary

UEA I stain

There are few or no capillaries immediately adjacent to the perimysium

UEA I stain

Endomysial Capillaries: Reduced numbers

Some muscle fibers have no adjacent capillary

UEA I stain

Endomysial Capillaries: Partial Denervation

UEA I stain
Endomysial capillaries
  Orientation: May be circumferential around muscle fibers (Above); Cut in cross-section
  Number: Every muscle fiber has several adjacent capillaries

UEA I stain

Endomysial Capillaries: Dermatomyositis with Vascular pathology (DM-VP)

Endomysial capillaries
  Orientation: Normal
  Number: Reduced or absent Endothelium (Ulex stain) in regions with small muscle fibers (Arrow)
    Endothelium is lost but basal lamina is still present
      & may have C5b-9 deposition
  Size: Increased in regions neighboring muscle fiber atrophy

UEA I stain

Endomysial Capillaries: Enlarged

UEA I stain

UEA I stain
Patient history: Cardiac failure & Interstitial lung disease

Endoneurial Microvessels

H&E stain
Endoneurial Microvessel (Arrow)
  Orientation: Along length of nerve

Toluidine blue stain

Endomysial & Endoneurial Capillaries: Thickened Walls

Ultrastructure: From Robert E Schmidt MD

Ultrastructure: From Robert E Schmidt MD
Endoneurial vessel in Nerve
Basal lamina: Multiple layers
Non-diagnostic muscle
Endomysial vessel in Muscle
Thickened wall: Homogeneous

From: Chunyu Cai

Basal lamina of Endoneurial microvessels
  Thickened; Homogeneous (Arrows)
Basal lamina of Endoneurial microvessel
  Normal (Arrow)

Capillaries: Walls have varied thickness
Capillaries with homogeneous thick walls

Humoral Immune Microvasculopathy

Associated Disorders

C5b-9 stain

C5b-9 Deposits on Endoneurial Microvessels

C5b-9 stain

C5b-9 stain
Control Nerve
C5b-9 Deposits
  On Endoneurial microvessels

Endoneurial Microvessel Pathology
  Vessel size: Large
  Vessel wall: Thick
  Endothelial cells: Large
  Basal lamina: Multi-layered

Muscle: C5b-9 Deposits
  On Endomysial capillaries
Control Muscle
Microvasculopathy: C5b-9 Deposits on many endomysial capillaries

Go to Moderate & large vessel vasculitis
Return to Neuromuscular Home Page
Return to Vasculitis

1. Acta Neuropathol 2000;100:445-450
2. Am J Physiol Heart Circ Physiol 2016 Jul 1