---

MITOCHONDRIAL DISEASE: ULTRASTRUCTURE

Ultrastructural features of mitochondria in mitochondrial disease

• Numbers
  • Increased
  • Clustered in subsarcolemmal & intermyofibrillar spaces
• Shape: Abnormal
• Size: Enlarged or Elongated (Normal < 3-4 sarcomeres in length)
• Cristae: Irregular; Deficient; Stacking; Whorling
• Granules: Electron dense; Spherical; Multiple
• Paracrystalline structures (Inclusions)
  • Have regular geometrical periodicity
  • Most specific morphologic abnormality
  • Commonly occur in fibers with mitochondrial proliferation
  • "Parking Lot"
    
  • May occur in muscle, liver or brain
• Also see: Ultrastructure
  • PEO, Large mtDNA deletion
  • IM-VAMP (IBM)
  • COX deficiency
    
  • MELAS

---

Muscle mitochondria with normal structure.

---

From: R Schmidt

Mitochondria
  Numbers: Increased
  Localization: Either side of Z-line
  Sizes: Small, Normal, or Large & Elongated

---

Mitochondrial myopathy: Subsarcolemmal accumulations of mitochondria

---

Mitochondrial myopathy: Enlarged whorled mitochondrion

---

Mitochondrial disease: Abnormal muscle mitochondria from a child

---

Mitochondrial inclusions

• Major protein in inclusions
  • Creatine kinase, mitochondrial
• Similar inclusions may occur in
  • Injured muscle cells
  • Dermatomyositis

---

Inclusions: Present in many mitochondria

---

Longitudinal sections of crystalloid inclusions

---

Cross sections of crystalloid inclusion

---

Cross sections of crystalloid inclusions

---

Cross section of dark crystalloid inclusion

---

Dense parallel cristae

---

---

PEO: Crystalloid Inclusions (Parking lot bodies)

---

Return to Mitochondrial syndromes
Return to Mitochondrial pathology
Return to Muscle biopsies

12/2/2025