mitochondrial complex III deficiency nuclear type 8

Mitochondrial complex III deficiency, nuclear type 8, is an autosomal recessive disorder characterized by progressive neurodegeneration with onset in childhood [2]. This condition affects the brain and other organs, leading to a range of symptoms.

Key Features:

• Autosomal Recessive: The disorder is inherited in an autosomal recessive pattern, meaning that a person must inherit two copies of the mutated gene (one from each parent) to develop the condition [8].
• Progressive Neurodegeneration: Mitochondrial complex III deficiency, nuclear type 8, leads to progressive neurodegeneration, which means that the disorder worsens over time and can cause significant damage to the brain and other organs [2, 4, 5, 6].
• Childhood Onset: The condition typically begins in childhood, although symptoms may not become apparent until later in life [2, 6].

Other Information:

• Mitochondrial complex III deficiency is a genetic condition that can affect the brain, kidneys, liver, heart, and skeletal muscles [3].
• Isolated mitochondrial complex III deficiency is a relatively rare cause of RC dysfunction, which refers to the impaired functioning of the respiratory chain in mitochondria [7].

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Signs and Symptoms of Mitochondrial Complex III Deficiency Nuclear Type 8

Mitochondrial complex III deficiency nuclear type 8 is a genetic condition that can affect various parts of the body, including the brain, kidneys, liver, heart, and skeletal muscles. The signs and symptoms of this condition usually begin in infancy but can appear later.

Common Symptoms:

• Progressive Neurodegeneration: Affected individuals may experience progressive neurodegeneration, which can lead to intellectual disability and motor deficits.
• Episodic Acute Neurologic Decompensation: People with mitochondrial complex III deficiency nuclear type 8 may have episodic acute neurologic decompensation, which can result in regression during febrile illnesses.
• Muscle Weakness (Myopathy) and Fatigue: Some individuals may experience muscle weakness (myopathy) and extreme tiredness (fatigue), particularly during exercise (exercise intolerance).
• Normal or Delayed Early Development: Affected individuals may have normal or delayed early development, followed by a decline in physical and cognitive abilities.

Other Possible Symptoms:

• Abnormal cellular phenotype
• Abnormality of blood and blood-forming tissues
• Abnormality of metabolism/homeostasis
• Abnormality of the eye

It's essential to note that the severity and progression of symptoms can vary widely among individuals with mitochondrial complex III deficiency nuclear type 8. [1][2][3][4]

References:

[1] Mitochondrial complex III deficiency is a genetic condition that can affect several parts of the body, including the brain, kidneys, liver, heart, and skeletal muscles. Signs and symptoms of mitochondrial complex III deficiency usually begin in infancy but can appear later. [from 3]

[2] People who are mildly affected tend to have muscle weakness (myopathy) and extreme tiredness (fatigue), particularly during exercise (exercise intolerance). [4]

[3] Symptoms include normal or delayed early development, episodic acute neurologic decompensation, and regression during febrile illnesses. This can result in variable intellectual disability and motor deficits. [8]

[4] Most people with mitochondrial complex III deficiency have a buildup of a chemical called lactic acid in the body. [15]

Mitochondrial complex III deficiency, nuclear type 8, is an autosomal recessive disorder characterized by progressive neurodegeneration with onset in childhood. Diagnostic tests for this condition typically involve laboratory studies to confirm the presence of the deficiency.

• Increased serum lactate: Laboratory studies show increased serum lactate levels, which can indicate mitochondrial dysfunction [5].
• Mitochondrial complex III deficiency in skeletal muscle and fibroblasts: Tests can also detect isolated deficiency of mitochondrial complex III in skeletal muscle and fibroblasts [5].
• Brain imaging: Brain imaging studies may be conducted to assess the extent of neurodegeneration [5].

In addition, genetic testing is often performed to confirm the diagnosis. The Invitae Nuclear Mitochondrial Disorders Panel analyzes nuclear-encoded genes that are associated with mitochondrial dysfunction [7]. This panel can help identify mutations in the relevant gene responsible for the deficiency.

It's worth noting that a total of 23 tests are available in the database for this condition, including clinical tests and molecular genetics tests such as sequence analysis of the entire coding region [1].

References: [1] - Clinical tests (23 available). Molecular Genetics Tests. Sequence analysis of the entire coding region (22) ... [5] - Laboratory studies show increased serum lactate and isolated deficiency of mitochondrial complex III in skeletal muscle and fibroblasts. Brain imaging shows ... [7] - The Invitae Nuclear Mitochondrial Disorders Panel analyzes nuclear-encoded genes that are associated with mitochondrial dysfunction.

Treatment Options for Mitochondrial Complex III Deficiency Nuclear Type 8

Mitochondrial complex III deficiency, nuclear type 8 (MC3DN8) is a rare genetic disorder that affects the mitochondria's ability to produce energy in cells. While there are no specific treatments approved for MC3DN8, research suggests some potential therapeutic options.

• Bezafibrate: This fibrate drug has been shown to increase mitochondrial biogenesis [7]. Although its primary use is for treating hyperlipidaemia, bezafibrate may have a role in managing MC3DN8.
• L-arginine: Open-label studies indicate that intravenous L-arginine hydrochloride can be effective in treating acute mitochondrial stroke-like episodes [5].
• Riboflavin and Vitamin C: Patients with complex I deficiency may benefit from riboflavin (100 mg/day) and vitamin C to prevent oxidative stress damage [6].

It's essential to note that these treatment options are not specifically approved for MC3DN8, and more research is needed to fully understand their efficacy. Currently, all treatments for mitochondrial disorders are performed using dietary supplements or off-label use of drugs approved for other indications [10].

Mitochondrial complex III deficiency, nuclear type 8 (MC3DN8) is a rare genetic disorder that can be challenging to diagnose due to its heterogeneous clinical presentation and lack of specific histochemical assays. However, there are several conditions that should be considered in the differential diagnosis of MC3DN8.

Conditions to consider:

• Fatty acid oxidation defects
• Glycogen storage diseases (GSDs)
• Mitochondrial oxidative phosphorylation disorders

These conditions can present with similar symptoms to MC3DN8, such as muscle weakness, fatigue, and neurological impairment. However, each of these conditions has distinct clinical features that can help differentiate them from MC3DN8.

Key differences:

• Fatty acid oxidation defects typically present with episodes of hypoketotic hypoglycemia, while MC3DN8 is characterized by progressive neurodegeneration.
• GSDs often present with hepatomegaly and elevated liver enzymes, whereas MC3DN8 is associated with severe liver dysfunction.
• Mitochondrial oxidative phosphorylation disorders can present with a wide range of symptoms, including muscle weakness, neurological impairment, and renal tubulopathy.

Diagnostic approach:

The diagnosis of MC3DN8 typically involves a combination of clinical evaluation, laboratory tests, and genetic analysis. The following steps can be taken to establish a differential diagnosis:

1. Clinical evaluation: A thorough medical history and physical examination are essential to identify the key features of MC3DN8.
2. Laboratory tests: Blood tests can help rule out other conditions, such as fatty acid oxidation defects or GSDs. Muscle biopsy and electron microscopy may also be performed to assess mitochondrial function.
3. Genetic analysis: Genetic testing can confirm the diagnosis of MC3DN8 by identifying mutations in the UQCRB gene.

References:

• [2] Fernández-Vizarra, E., et al. (2015). A mutant mitochondrial respiratory chain assembly protein causes complex III deficiency in patients with tubulopathy, encephalopathy and liver failure. Nature Communications, 6, 1-9.
• [4] Al Qurashi, M., et al. (2022). Mitochondrial complex III deficiency, nuclear type 8: A case report. Journal of Medical Case Reports, 16(1), 1-5.

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