Neuromuscular

TYPE II MUSCLE FIBER ATROPHY

Clinical features
Congenital
Disuse
Early
Pathological features


Myosin ATPase, pH 9.4

Disuse: Type II muscle fiber atrophy








Myosin ATPase, pH 9.4

NADH

Type 2 Atrophy: Early


Myosin ATPase, pH 4.6
Type IIB atrophy

Myosin ATPase, pH 9.4
Narrow, elongated muscle fiber

Congenital type II atrophy


Myosin ATPase, pH 9.4

Type II atrophy: Clinical features

Type II atrophy: Pathology

  • Type II (dark at pH 9.4) Muscle fibers
    • Small: Reduced cross-sectional area\
    • Shape: Angular
    • Early changes
      • Atrophy in type IIB (Intermediate staining at pH 4.6) fibers
      • Narrow elongated muscle fibers
    • Disuse & weight loss atrophy: Small fibers are angular
    • Congenital: Small fibers are polygonal or rounded
  • Type I (lighter at pH 9.4) Muscle fibers
    • Larger than type II
    • Often atrophic compared to normal type 1 fibers
  • NADH stain: Small fibers usually pale
  • Nuclei
    • Number: Unchanged
    • Myonuclear domain size: Reduced
  • Recovery of fiber size after Disuse atrophy 1
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


12/9/2014