Neuromuscular

MYASTHENIA GRAVIS: Muscle Pathology

NMJs
  MG - Abnormal
  Normal
  Proteins
Myasthenia gravis
  Chronic, Undertreated
  Congenital
    AChE deficiency
    AChR mutation
  Diagram
  Lymphorrhages
  Pathological features
  Pathophysiology
  Rippling muscles & Thymoma

Neuromuscular Junctions: Myasthenia Gravis

NMJ Congenital MG
Esterase stain
Small, pale neuromuscular junction from patient with
congenital myasthenia gravis.



NMJ MG    
 



Esterase stain
Small, pale and multi-segmented neuromuscular junctions from patients with acquired myasthenia gravis.



Normal NMJ  
Esterase stain
Neuromuscular junctions: Normal

Lymphorrhages

Lymphorrhage  
H&E stain


H&E stain

Lymphorrhages from patients with myasthenia gravis and thymoma.

Myasthenia Gravis: Muscle pathology 1


NEUROMUSCULAR JUNCTION ANATOMY: NORMAL & MYASTHENIA GRAVIS


From Drachman

Myasthenia gravis: Chronic, Undertreated



H&E stain
Varied muscle fiber size: Atrophy & Hypertrophy
Pyknotic nuclear clumps

H&E stain


Esterase stain
Neuromuscular Junctions: Small, Irregular & Pale stained

Esterase stain


ATP pH 9.4 stain
Fiber types
  Type 2 predominance
  Small are type 2
  Large are type 1 (Above) or 2 (Below)

ATP pH 9.4 stain

Fiber types: Scattered type 2C fibers (Intermediate staining) are present

ATP pH 4.3 stain

Myasthenia gravis, Congenital: AChE deficiency



H&E stain
Muscle, Motor points (Areas with NMJs; Above = Top left & Bottom right near spindle)
  Endomysium: Mildly increased
  Muscle fibers: Enlarged nuclei (Below right)

H&E stain


Gomori trichrome stain
Muscle, Motor points
  Endomysium: Mildly increased
  Muscle fibers: Coarse internal architecture (Above)
  Intramuscular nerves: Normal (Below)

VvG stain

Fiber types: Type 1 (pale) muscle fiber predominance

ATP pH 9.4 stain


Esterase stain
Neuromuscular Junctions
  Very Pale stained (Above; Arrows)
  Some of the palest NMJs have neighboring acid phosphatase staining (Below; Arrows)

Acid phosphatase stain

Myasthenia gravis, Thymoma & Rippling muscle syndrome


H&E stain
Muscle fibers: Occasional area with regenerating muscle fibers (Above)
Normal muscle fibers: In most areas (Below)

H&E stain

Perimysial vessel: Associated inflammation extending into the endomysium

H&E stain


VvG stain
Inflammation around intermediate-sized vessels
  Mostly mononuclear cells
  Few cells stain for acid phosphatase (Below)

Acid phosphatase stain


Esterase stain
Neuromuscular Junctions
  Size: Small or Elongated
  Intensity of staining: Normal

Esterase stain

Caveolin-3
  Variably reduced or normal on muscle fiber surfaces

Caveolin-3 stain

MHC, Class I
  Abnormally upregulated on muscle fiber surfaces & cytoplasm in some regions

MHC Class I stain


References
1. Neuropathology and Applied Neurobiology 2009;35:103110

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10/2/2012