Normal adult
Normal child
Immaturity & Regeneration
Central cores
Moth-eaten fibers
Lobulated fibers
Ring fibers
Split fibers
Target fibers
Tubular aggregates
  Small angular fibers
Trabecular myopathy

Normal internal architecture: Adult

Muscle fibers: Type correspondence
  Darkest fibers: Type I
  Palest fibers: Type 2A
  Intermediate fibers: Type 2B


Normal internal architecture: Child

  Staining patterns: Coarser than in adults

Neonate: 1 week of age

Infant: 1 year of age

Immature (Regenerating) muscle fibers

Internal architecture: Coarser and darker than in normal fibers in adults
Size: Often intermediate
Shape: Polygonal or Rounded

Linearization of sarcoplasmic membranes in pale (Type 2) muscle fibers

  Clinical correlations
    Mostly non-specific
    Common, & more severe, in: Myophosphorylase deficiency & Glycogen storage.

Internal architecture: Linear (White arrow) & less punctate compared to control muscle fibers (Dark arrow)

Linearization of Internal architecture: More severe

  Dark streaks of NADH staining in paler (Type 2) muscle fibers
Linearization of internal architecture
  Mostly in paler fibers
  One small dartk muscle fiber is a pyknotic nuclear clump (from denervation without reinnervation

Linearization of Internal architecture: Other stains

Linearization: Visible as cracks in type 2 (Darker stained) muscle fibers

ATPase pH 9.4 stain

Linearization: Visible as black-stained linear regions in muscle fibers

VvG stain

Motheaten muscle fibers

NADH stain

Lobulated Muscle Fibers

Abnormal internal architecture: Moth-eaten & Lobulated muscle fibers
  Dark, irregularly stained fibers are: Moth-eaten, Lobulated or Trabecular
  More common in type 1 muscle fibers
  May occur in myopathy or neuropathy.
  Myopathies commonly with lobulated fibers: LGMD 2A; Ullrich CMD; Bethlem myopathy

NADH stain
Lobulated Muscle Fibers: Patient with cachexia & muscle fiber atrophy

NADH stain

NADH stain
Lobulated Muscle fibers

NADH stain

Lobulated Muscle Fibers: Other stains

VvG stain

Cachexia: Abnormal nuclear morphology

Congo red stain

See NADH stain methodology

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