Neuromuscular

MUSCLE FIBER TYPES


Abnormal muscle with many scattered Immature muscle fibers

2C fibers
Disorders
MYH components
  Control muscle
  ALS
Staining: Histochemistry


Muscle Fiber Types


ATPase pH 4.3
ATPase pH 4.3 stain

ATPase pH 4.3 stain


ATPase pH 4.6 stain
ATPase pH 4.6 stain

ATPase pH 4.6 stain


ATPase pH 9.4 stain
ATPase pH 9.4 stain

ATPase pH 9.4 stain

Type 2C (Immature) muscle fibers


Type 2C muscle fibers: Increased numbers (Same muscle biopsy as above) with normal fiber morphology
  Fiber size: Mild variation
  No regenerating, or morphologically immature, muscle fibers

H&E stain

VvG stain
Internal architecture
  Unremarkable
  Rare internal nucleus

Gomori trichrome stain


MYH stains = Green; Collagen IV = Red

ALS Muscle: Fiber Types

Type 1 fibers: Normal
  ATPase: Intermediate color at pH 9.4 & Dark at pH 4.6 & 4.3
  All have MYH7, but not MYH2 or MYH1
Type 2 fibers: Variant
  All have MYH2 & moderate MYH7
Type 2A fibers
  All have MYH2 & Moderate MYH7, but no MYH1
  ATPase: Dark at pH 9.4; Pale at pH 4.6 & 4.3
Type 2B fibers
  All have MYH2 & Moderate MYH7 & MYH1
  ATPase: Dark at pH 9.4; Intermediate at 4.6; Pale at pH 4.3
Type 2C fibers
  All have MYH2 & MYH7, but no MYH1
  ATPase: Moderately Dark at pH 9.4 & 4.6; Internediate at pH 4.3

MYH stains = Green; Collagen IV = Red


MYH stains = Green; Collagen IV = Red


MYH stains = Green; Collagen IV = Red

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11/15/2021