Neuromuscular

DYSMYELINATION
Metachromatic Leukodystrophy (MLD) (& Krabbe)

Histochemistry
Myelin sheath thin: TB; EM
Onion bulbs
Prismatic inclusions (Macrophages)
Schwann cell debris
Tuffstone bodies

Metachromatic Leukodystrophy (MLD)


Hypomyelinated axons


Metachromatic Leukodystrophy (MLD)
  Myelinating Schwann cells
    Contain cytoplasmic particulate & clear debris.

  Axons surrounded by
    Thin myelin sheaths & Onion bulbs, small.

Myelinating Schwann cells
  Contain particulate & clear debris in cytoplasm
Onion Bulbs: Small








H&E stain
Endoneurium
  Pale
  Increased space between axons

H&E stain


Gomori trichrome stain
Reduced staining for myelinated axons

Gomori trichrome stain

Larger axons
  Increased space between axons

VvG stain

Larger axons: Normal to mildly reduced numbers
Smaller axons: Reduced numbers in some endoneurial areas

MLD: Reduced or Absent Myelin Sheath

Unmyelinated axons: Surrounded by Schwann cells

Axons with thin, or folded, myelin sheath
Onion bulb: Small, single layer of basal lamina around axons & Schwann cells

MLD: Schwann cell inclusions

Axons: Moderately or Severely thin myelin sheath
Schwann cells: Contain myeloid debris in secondary lysosomes

Schwann cells: Cytoplasm contains Tuffstone inclusions & Myeloid debris

Schwann cells with Cytoplasmic inclusions

MLD: Tuffstone Bodies

Tuffstone bodies
  Electron dense
  Most common in Schwann cells of myelinated & unmyelinated axons
  Contain irregularly oriented material
  5.8 nm periodicity
  May have peripheral lamellae oriented perpendicular to surface

Tuffstone bodies

MLD: Macrophages

Prismatic inclusions
  Commonly in endoneurial macrophages
  Stacks of lamellar disks

MLD: Muscle

Muscle fiber sizes: Mild variation; No denervation

Muscle fiber types
  Fiber type grouping: Mild
  Type 2C: Increased numbers

Krabbe disease: Globoid cells


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6/16/2016