SCOT deficiency

Alternate names

Succinyl-CoA:3-oxoacid CoA transferase deficiency; Ketoacidosis due to SCOT deficiency; Succinyl-CoA acetoacetate transferase deficiency; 3-oxoacid CoA transferase deficiency

Definition

SCOT deficiency is a metabolic disease that is caused by reduced or missing levels of an enzyme called succinyl-CoA:3-ketoacid CoA transferase (SCOT).

Summary

Succinyl-CoA:3-ketoacid CoA transferase (SCOT) enzyme is necessary for the body to use ketones. Ketones are substances produced in the liver when fats are broken down. Ketones are an important source of energy, especially when there is a shortage of carbohydrates (sugar). SCOT deficiency is characterized by episodes of ketoacidosis (build-up of ketones in the body).

Epidemiology

The prevalence of SCOT deficiency is unknown. More than 20 cases of this condition have been reported in the scientific literature.

Cause

Mutations in the OXCT1 gene cause SCOT deficiency. The OXCT1 gene provides instructions for making an enzyme called succinyl-CoA:3-ketoacid CoA transferase (SCOT). The SCOT enzyme is made in the energy-producing centers of cells (mitochondria). The enzyme plays a role in the breakdown of ketones, which are an important source of energy during fasting or when energy demands are increased, such as during illness or when exercising.

Gene mutations

OXCT1 gene mutations result in the production of a SCOT enzyme with little or no function. A reduction in the amount of functional enzyme leads to an inability to break down ketones, resulting in decreased energy production and an elevated level of ketones in the blood. If these signs become severe, a ketoacidotic attack can occur. Individuals with mutations that create an enzyme with partial function are still prone to ketoacidotic attacks, but are less likely to have persistent ketosis.

Inheritance

Autosomal recessive inheritance, a 25% chance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

• The signs and symptoms of SCOT deficiency typically appear within the first few years of life.
• Affected individuals experience episodes of extreme tiredness (lethargy), appetite loss, vomiting, rapid breathing, and, occasionally, seizures.
• These episodes, which are called ketoacidotic attacks, sometimes lead to coma.
• About half of affected individuals have a ketoacidotic attack within the first 4 days of life. Affected individuals have no symptoms of the disorder between ketoacidotic attacks.
• People with SCOT deficiency usually have a permanently elevated level of ketones in their blood (persistent ketosis). If the level of ketones gets too high, which can be brought on by infections, fevers, or periods without food (fasting), a ketoacidotic attack can occur. The frequency of ketoacidotic attacks varies among affected individuals.

Diagnosis

• SCOT deficiency is diagnosed when a child presents with symptoms of the disease during a ketoacidotic crisis.
• A healthcare provider will then typically complete a series of laboratory tests to rule out other diseases that can cause similar symptoms. Levels of SCOT enzyme can be measured by testing the cells of the skin (fibroblasts).
• If these enzyme levels are low, it indicates that a child has SCOT deficiency.
• Genetic testing of the OXCT1 gene can be used to confirm the diagnosis.

Treatment

The treatment for SCOT deficiency is based on trying to avoid ketoacidotic crises, as these are the only times that symptoms of the disease occur. Because ketoacidotic crises occur when all of the glucose from a meal is broken down, it is important for people with SCOT deficiency to eat frequent meals with large amounts of carbohydrates. It is also important for people with SCOT deficiency to avoid eating food with high fat content. Doctors may recommend that people with the disease avoid high-protein meals as well. Individuals with SCOT deficiency can monitor levels of ketones in the urine in order to make sure they are not too high. Oral sodium bicarbonate supplements can be used in times of stress, such as an illness, to make sure that the body is receiving enough energy from other forms. If a ketoacidotic crisis does occur, it is important that people with SCOT deficiency receive treatment right away. People with this disease typically respond well to IV infusions of glucose and sodium bicarbonate during times of ketoacidotic crisis.

Prognosis

• The long-term outlook for children with SCOT deficiency can vary. For some children, the initial presentation of symptoms can be very severe. If a diagnosis of SCOT deficiency and treatment is not received, the initial symptoms can be fatal. In some cases, people with SCOT deficiency may develop heart problems. As children get older, the frequency of episodes tends to decrease.
• If the recommended diet is followed and precautions are taken during times of stress on the body such as illness, the long-term outlook for people affected by SCOT deficiency is good. With proper management, children with SCOT deficiency are expected to reach their developmental milestones at the appropriate age, and intellectual disability is not known to be associated with the disease. A good outcome is predicted even in individuals who have multiple ketoacidotic crises.

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NIH genetic and rare disease info

• NIH info on SCOT deficiency

SCOT deficiency is a rare disease.

SCOT deficiency Resources
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