Neuromuscular

Hereditary Neuropathy with Liability to Pressure Palsies (HNPP)



HNPP Nerve: Frozen sections

Axon Loss: Reduced numbers of myelinated axons

Gomori trichrome stain

VvG stain

HNPP Nerve: Fixed


Toluidine blue stain
Reduced numbers of large axons
Abnormal myelination of axons includes
  Hypomyelination
  Abnormally folded (Tomaculae) or shaped myelin sheaths
Small onion bulbs are also present (Below; Arrow)


Toluidine blue stain

Toluidine blue stain


Toluidine blue stain





Thickened myelin sheath due to multiple layers of folded myelin




Folding of myelin sheath
  Outside axon or invaginating into axon

Thickened & folded myelin sheath
Peripheral Schwann cell nucleus

Two axons with tomaculae
One thinly myelinated large axon

HNPP: Axons & Myelin components

Most myelinated axons are small
Compare to Normal nerve
  Myelinated axons are large & small

Neurofilament stain (Green)
P0 stain (Red)


Neurofilament stain (Green)
Myelin basic protein stain (Red)
HNPP: MBP is in myelin sheaths around small axons
Compare to Normal nerve
  MBP is only in sheaths around large axons

HNPP: MBP is in most myelin sheaths
Compare to Normal nerve
  MBP is only in sheaths around large axons
  P0 is in myelin sheaths around small & large axons

P0 stain (Green)
Myelin basic protein stain (Red)


Neurofilament (SMI31) stain
Axon Loss
  Reduced numbers of large axons
  Relative preservation of numbers of small axon

HNPP: Muscle


Gomori trichrome stain
Mild atrophy


H& E stain
Occasional: Grouped atrophy & Pyknotic nuclear clumps


ATPase pH 9.$ stain
Fiber type grouping


ATPase pH 4.3 stain
Fiber type grouping; Rare Type 2C muscle fiber


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Return to Demyelination: Chronic
Return to Nerve biopsy: Normal
Return to Biopsy: Pathology index
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Return to Demyelinating neuropathies
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9/19/2016