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Congenital MG: Rapsyn mutations

H&E stain

Muscle fibers
  Varied sizes

H&E stain

Muscle fibers: Varied sizes
  Small fibers
    Shapes: Angular, Polygonal or Rounded
    Size: Intermediate

H&E stain

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Gomori trichrome stain

Muscle fibers
  Varied sizes
Intramuscular nerves: Normal

VvG stain

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NADH stain

Internal architecture: Coarse in most muscle fibers

NADH stain

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ATPase pH 9.4 stain

Fiber types
  Type I predominant
  Type II fibers: Tend to be smaller
  Type 2C fibers: Few scattered

ATPase pH 4.3 stain

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Esterase stain

Neuromuscular Junctions
  Pale
  Thin
  May be multisegmented

Esterase stain

Esterase stain

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7/23/2026