Small vessel vasculopathy

Small Vessel Pathology (Capillaries or Endoneurial Microvessels) ²

Capillaries
Muscle: Normal
Endoneurial Microvessels
Capillary pathology
Microvasculopathy
C_5b-9 Deposits
Enlargement
Pipestem
SRP Myopathy
TS-HDS neuropathy
Endoneurial inflammation
Ipilimumab
Perineuritis
Loss
DM-VP
GvHD
Subperineurial edema
Thickened vessel walls

Endomysial Capillary: Normal

ENDOMYSIAL CAPILLARIES: 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)
Composition
Collagen IV
Laminin
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
Contractile
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 C_5b-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
Diabetes 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) Capillary walls thick: Differential diagnosis ¹ Increased age Gastrocnemius muscle Diabetes Chronic idiopathic axonal neuropathies CMT I Hypoxia M-protein related neuropathy TS-HDS antibody-related polyneuropathy: Pathology Amyloid		Basal lamina of Endoneurial microvessel Normal (Arrow)