Neuromuscular

TYPE II MUSCLE FIBER ATROPHY

Clinical features
Pathology
  Features
  Childhood
  Early
    Elongated fibers
    2B fiber atrophy
  Moderately severe
Atrophy: General

ATPase pH 9.4 stain

Type II atrophy: Pathology


Type II Muscle Fiber Atrophy: Clinical associations


Type 2 Muscle Fiber Atrophy: Moderately Severe


H&E stain
Muscle fiber sizes
  Bimodal distribution
  Type 1 (Larger) muscle fibers are normal or somewhat small
Small muscle fibers
  Shape: Often angular; Some are elongated
  Distribution: May appear clustered

H&E stain

VvG stain

ATPase pH 9.4 stain
Small muscle fibers
  Usually Type 2 (Dark stained at ATPase pH 9.4)
  Shape: Often angular; Some are narrow and elongated
  Distribution: May appear clustered

ATPase pH 9.4 stain

ATPase pH 4.3 stain
Small muscle fibers: Type 2
  Pale stained at ATPase pH 4.6 & 4.3

ATPase pH 4.6 stain

NADH stain
Type 2 muscle fibers: Other stains
  NADH: Pale
  COX: Pale
  Esterase: Not dark

Esterase stain

PAS stain
Type 2 muscle fibers: Other stains
  PAS: Darker
  Phosphorylase: Darker

Phosphorylase stain

Type 2 Atrophy: Early


H&E stain
Type 2 muscle fibers
  Elongated
  Narrow

H&E stain

Gomori trichrome stain
Type 2 muscle fibers
  Elongated
  Narrow

Congo red stain

Congo red stain

ATPase pH 9.4 stain
Type 2 muscle fibers
  Shapes
    Elongated & Narrow
    Intermediate-sized & Polygonal

ATPase pH 9.4 stain

ATPase pH 4.3 stain
Atrophy: Type 2 muscle fibers
  Small & Angular
  Pale stained with ATPase pH 4.3
  Smallest muscle fibers may be 2B (Intermediate stain with ATPase pH 4.6)

ATPase pH 4.6 stain
Type 2B Muscle Fiber Atrophy

ATPase pH 4.6 stain


H&E stain
Atrophy: Type 2 muscle fibers
  Elongated
  Narrow

H&E stain

VvG stain

Congo red stain

NADH stain

ATPase pH 9.4 stain
Type 2 muscle fibers: Atrophy
  Shapes: Elongated; May wrap abound larger type 1 fibers

ATPase pH 9.4 stain
   
ATPase pH 9.4 stain
Type 2 Atrophy

ATPase pH 4.6 stain
Type IIB atrophy


Childhood type II atrophy

Type 2 muscle fibers
  Small
  Polygonal or Round

H&E stain
Fiber size distribution: Bimodal, Large & Small
Small muscle fibers: Polygonal or Round

H&E stain

Gomori trichrome stain
Fiber size distribution: Bimodal, Large & Small
Small muscle fibers: Polygonal or Round

ATPase pH 9.4 stain
Fiber size distribution: Small muscle fibers dark stained (Type 2)
Small muscle fibers: Polygonal or Round

ATPase pH 9.4 stain

ATPase pH 9.4

ATPase pH 4.3 stain
Type 2 muscle fibers
  Pale stained
  Type 2A & 2B

ATPase pH 4.6 stain

NADH stain
Type 2 muscle fibers
  Pale on NADH, SDH & COX stain

Cytochrome oxidase (COX) stain

SDH stain

Type 2 muscle fibers
  Darker on PAS stain

PAS stain

See
  Fiber type disorders
  Fiber type properties

Return to Neuromuscular Home Page
Return to Myopathies with wasting

References
1. Am J Physiol Cell Physiol 2012; Online August
2. Am J Physiol Cell Physiol 2015;308:C932-943
3. Muscle Nerve 2017;56:122-128

5/21/2021