Small Vessel Pathology (Capillaries or Endoneurial Microvessels) 2

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


Capillary Structure

Endothelial cells (E)
  Surround lumen
  Stain: UEA
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
  Location: Within basla lamina
  Stain: PDGRFβ

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

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

C5b-9 Deposits on Endoneurial Microvessels & Endomysial Capillaries
Control Nerve
C5b-9 Deposits
  On Endoneurial microvessels & Endomysial capillaries
Control Muscle

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