Muscle fiber atrophy: Perifascicular distribution

• Smallest (atrophic) muscle fibers are located near regions of "avascular" perimysium
  • Muscle fibers near perimysial vesels are larger.
• Atrophic muscle fibers near the "avascular" perimysium have abnormal internal architecture, but not necrotic.
• Abnormal internal architecture: See
  • H & E
  • Gomori trichrome
  • NADH
  • Mitochondria
•   Necrotic and regenerating fibers are more common in DM-like disorders in adults (IMPP).
• Nuclei in small muscle fibers are enlarged and commonly internal.