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mitochondrial myopathy
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 [1]
- most mitochondrial myopathies occur before the age of 20
Pathology:
- muscle biopsy
a) Gomori trichrome stain will show ragged red fibers (due to abnormal mitochondria)
b) biochemical anlaysis of muscle biopsy specimen for specific enzymatic activity
Genetics:
- maternal transmission
- associated with defects in MT-CYB
Clinical manifestations:
1) extraocular muscle palsy
- progressive external ophthalmoplegia
2) blindness, cataracts, retinitis pigmentosa
3) droopy eyelids
4) muscle weakness or exercise intolerance is often 1st symptom
5) heart failure
6) cardiac arrhythmias
7) mental retardation, dementia
8) movement disorders
9) stroke-like episodes
10) deafness
11) vomiting
12) seizures
13) headache
Laboratory:
1) serum creatine kinase may be elevated
2) serum lactate: lactic acidosis
3) urine myoglobin: myoglobinuria
Management:
1) no specific treatment for any of the mitochondrial myopathies
2) physical therapy may extend the range of movement of muscles & improve dexterity
3) riboflavin, coenzyme Q, & carnitine may subjectively improve fatigue in some patients.
4) prognosis varies
a) depends on disease & the degree of organ involvement
b) progressive weakness to death
Related
mitochondrial myopathy gene mutation
Specific
mitochondrial encephalomyopathy
General
metabolic myopathy
mitochondrial disease
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, 17.
American College of Physicians, Philadelphia 1998, 2015
- National Institute of Neurological Disorders and Stroke (NINDS)
NINDS Mitochondrial Myopathies Information Page
https://www.ninds.nih.gov/Disorders/All-Disorders/Mitochondrial-myopathy-Information-Page