mitochondrial myopathy

Introduction

A group of neuromuscular diseases caused by damage to the mitochondria.

Etiology

• abnormality of oxidative phosphorylation in skeletal muscle

Epidemiology

• prevalence is 0.006-0.016% of population
• most mitochondrial myopathies occur before the age of 20

Pathology

• muscle biopsy
  • Gomori trichrome stain will show ragged red fibers (due to abnormal mitochondria)
  • biochemical anlaysis of muscle biopsy specimen for specific enzymatic activity

Genetics

• maternal transmission
• associated with defects in MT-CYB

Clinical manifestations

• extraocular muscle palsy
  • progressive external ophthalmoplegia
• blindness, cataracts, retinitis pigmentosa
• droopy eyelids
• muscle weakness or exercise intolerance is often 1st symptom
• heart failure
• cardiac arrhythmias
• mental retardation, dementia
• movement disorders
• stroke-like episodes
• deafness
• vomiting
• seizures
• headache

Laboratory

• serum creatine kinase may be elevated
• serum lactate: lactic acidosis
• urine myoglobin: myoglobinuria

Management

• no specific treatment for any of the mitochondrial myopathies
• physical therapy may extend the range of movement of muscles & improve dexterity
• riboflavin, coenzyme Q, & carnitine may subjectively improve fatigue in some patients.
• prognosis varies
  • depends on disease & the degree of organ involvement
  • progressive weakness to death

More general terms

• metabolic myopathy
• mitochondrial disease

More specific terms

• mitochondrial encephalomyopathy

Patient information

mitochondrial myopathy patient information