Disuse: Type II muscle fiber atrophy
Myosin ATPase, pH 9.4
|
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
|
|
Clinical features
- Weakness: Proximal > Distal; Symmetric
- Muscle size: Wasting > Weakness
- Associated disorders
- Weight loss: > 15%
- Disuse
- Aging
- Systemic disease
- Childhood
Pathology
- Type II (dark at pH 9.4): Muscle fibers are small
- 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 are larger than type II
- NADH stain: Small fibers usually pale
|
