Muscle Necrosis

• Necrosis of an entire myofibre is uncommon
• Segmental necrosis is more typical
• Muscle cell contents may leak into the blood if the cell membrane is damaged
• Creatine kinase (CK) is an enzyme which leaks following injury
  • Used to measure the extent of muscle damage
• Often is followed by regeneration
• Histologically:
  • Hyaline hypercontracted fiber rounded at cross-section and increased diameter and eosin staining
    • May also be an artifact due to hypercontraction of normal fibres at fixation
  • Fragmenting portions of fibre -> floccular or granular
  • Normal portion of fibre may detach from necrotic part -> retraction caps
  • Infarction may cause discoid degeneration - necrotic fibres detach at Z lines
  • May mineralise
• Zenker's degeneration - secondary to systemic disease
  • Scattered small segments of necrosis and fast regeneration
  • Sacrolemmal tubes are intact