Mitochondrial complex II deficiency

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Obesity, Sleep & Internal medicine
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Mitochondrial complex II deficiency
Synonyms	Succinate dehydrogenase deficiency
Pronounce	N/A
Specialty	Medical genetics
Symptoms	Muscle weakness, hypotonia, encephalopathy, cardiomyopathy, seizures
Complications	N/A
Onset	Infancy or childhood
Duration	Chronic
Types	N/A
Causes	Mutations in SDHA, SDHB, SDHC, SDHD genes
Risks	Genetic predisposition
Diagnosis	Genetic testing, muscle biopsy, metabolic testing
Differential diagnosis	Leigh syndrome, Mitochondrial complex I deficiency
Prevention	N/A
Treatment	Supportive care, vitamin supplementation
Medication	N/A
Prognosis	Variable, depending on severity
Frequency	Rare
Deaths	N/A

Mitochondrial Complex II Deficiency is a rare metabolic disorder that affects the function of mitochondria, the energy-producing structures within cells. This condition is characterized by a deficiency in the activity of Complex II, also known as succinate dehydrogenase (SDH), which is part of the electron transport chain in mitochondria.

Pathophysiology

Complex II is unique among the complexes of the electron transport chain because it is the only one that participates in both the citric acid cycle and the electron transport chain. It catalyzes the oxidation of succinate to fumarate and transfers electrons to ubiquinone. A deficiency in Complex II disrupts this process, leading to impaired energy production and an accumulation of metabolic intermediates.

Clinical Presentation

Patients with mitochondrial complex II deficiency may present with a variety of symptoms, which can include muscle weakness, hypotonia, developmental delay, and failure to thrive. The severity and range of symptoms can vary widely among affected individuals.

Genetic Basis

Mitochondrial complex II deficiency is often caused by mutations in one of the four nuclear genes that encode the subunits of succinate dehydrogenase: SDHA, SDHB, SDHC, and SDHD. These mutations can be inherited in an autosomal recessive manner.

Diagnosis

Diagnosis of mitochondrial complex II deficiency typically involves a combination of clinical evaluation, biochemical testing, and genetic analysis. Biochemical tests may show reduced activity of succinate dehydrogenase in muscle or liver tissue samples.

Treatment

Currently, there is no cure for mitochondrial complex II deficiency. Treatment is primarily supportive and may include nutritional supplements, physical therapy, and management of symptoms. Research into potential therapies is ongoing.

See Also

• Mitochondrial disease
• Electron transport chain
• Succinate dehydrogenase
• Metabolic disorder