197. Mitochondrial Myopathies Flashcards
What do mitochondria produce by oxidative phosphorylation?
Adenosine triphosphate (ATP)
ATP is the essential cellular energy substrate.
What are the products used in the electron transport chain for ATP production?
NADH and FADH2
NADH is produced from the Krebs cycle and fatty acid oxidation.
Name the five enzyme/protein complexes involved in the electron transport chain.
- Complex I (NADH dehydrogenase)
- Complex II (succinate dehydrogenase)
- Coenzyme Q
- Complex III
- Complex IV (cytochrome c oxidase)
- Complex V
These complexes are located on the inner mitochondrial membrane.
What clinical presentations result from abnormalities in mitochondrial electron transport chain complexes?
Decreased organ bioenergetic capacity, including myopathies and encephalopathies
Acidosis also results from overproduction of lactate and pyruvate.
How are mitochondrial disorders inherited?
Usually maternal but can be sporadic
Mitochondria are inherited from the mother through the ova.
What concept explains the varied clinical expressions of mitochondrial disorders?
Heteroplasmy
Heteroplasmy refers to the presence of both normal and mutant mtDNA in cells.
What are the two types of genetic sequences encoding the enzyme/protein complexes in mitochondria?
- Nuclear genome (nDNA)
- Mitochondrial genome (mtDNA)
Mutant mtDNA can coexist with normal mtDNA.
What are the potential effects of mitochondrial disorders on organ systems?
They can affect every organ system
Mitochondria are involved in various metabolic and regulatory functions.
What are the symptoms of childhood onset mitochondrial disorders?
- Acute onset of cyanosis
- Seizures
- Temperature instability
- Myopathies
- Encephalopathy
These disorders severely impact neurologic development.
Which syndrome may include hypertrophic cardiomyopathy in childhood onset mitochondrial disorders?
MELAS
MELAS stands for mitochondrial encephalopathy with lactic acidosis and stroke-like episodes.
What are some symptoms of adult onset mitochondrial disorders?
- Weakness
- Myopathies
- Droopy eyelids
- Limited mobility of the eyes
- Cardiomyopathies
- Arrhythmias
- Dysphagia
- Gastrointestinal dysmotility
- Vomiting
These symptoms arise from decreased bioenergetic capacity.
True or False: Patients with mitochondrial myopathy have an increased susceptibility to malignant hyperthermia (MH).
False
Literature does not indicate an increased susceptibility to MH in most patients with mitochondrial myopathy.
Which muscle relaxant should be avoided in patients with mitochondrial disorders?
Succinylcholine
Succinylcholine has been associated with rhabdomyolysis and hyperkalemia cardiac arrest.
What should be avoided to reduce the risk of metabolic crisis in patients with mitochondrial disorders?
Acidosis
Metabolic crisis can be caused by low blood sugar and buildup of toxic substances.
What are some signs of metabolic crisis?
- Nausea
- Vomiting
- Diarrhea
- Extreme somnolence
- Irritable mood
- Behavior changes
If untreated, symptoms can escalate to respiratory insufficiency and seizures.
