Succinyl-CoA:3-ketoacid CoA transferase deficiency

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency is an inherited disorder that impairs the body's ability to break down ketones, which are molecules produced in the liver during the breakdown of fats.

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.

ORPHANET DEFINITION A rare, genetic disorder in ketone body utilization characterized by severe, potentially fatal intermittent episodes of ketoacidosis.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal recessive

Frequency in the source

From: MedlinePlus Genetics, National Library of Medicine

Reported case(s): 32.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Ketoacidosis · Very frequent (99-80%)

Acidosis resulting from accumulation of ketone bodies.

Reduced succinyl-CoA:3-oxoacid-CoA transferase activity in cultured fibroblasts · Very frequent (99-80%)

Activity of succinyl-CoA:3-oxoacid-CoA transferase (SCOT, or OXCT1; EC 2.8.3.5) below the lower limit of normal in cultured fibroblasts.

Hyperketonemia · Frequent (79-30%)

An increase in the level of ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone) in the blood.

Ketonuria · Frequent (79-30%)

High levels of ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone) in the urine. Ketone bodies are insignificant in the blood and urine of normal individuals in the postprandial or overnight-fasted state.

Tachypnea · Frequent (79-30%)

Very rapid breathing.

Vomiting · Frequent (79-30%)

Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions.

Cardiomegaly · Occasional (29-5%)

Increased size of the heart, clinically defined as an increased transverse diameter of the cardiac silhouette that is greater than or equal to 50% of the transverse diameter of the chest (increased cardiothoracic ratio) on a posterior-anterior projection of a chest radiograph or a computed tomography.

Coma · Occasional (29-5%)

The complete absence of wakefulness and consciousness, which is evident through a lack of response to any form of external stimuli.

Decreased body weight · Occasional (29-5%)

Abnormally low body weight.

Hypotonia · Occasional (29-5%)

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

Lethargy · Occasional (29-5%)

A state of fatigue, either physical or mental slowness and sluggishness, with difficulties in initiating or performing simple tasks. Distinguished from apathy which implies indifference and a lack of desire or interest in the task. A person with lethargy may have the desire, but not the energy to engage in personal or socially relevant tasks.

Nausea · Occasional (29-5%)

A sensation of unease in the stomach together with an urge to vomit.

Dehydration · Occasional (29-5%)

Failure to thrive in infancy · Occasional (29-5%)

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

Infancy; Neonatal

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal recessive

Frequency and the population described

From: MedlinePlus Genetics, National Library of Medicine

Reported case(s): 32.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal recessive pattern usually involves disease-causing changes in both copies of a gene. Parents may each carry one altered copy without having the condition themselves. A genetic counsellor can explain carrier testing and reproductive implications using the actual laboratory findings, rather than the condition name alone.

Which doctor should you see?

The suggested department for discussing Succinyl-CoA:3-ketoacid CoA transferase deficiency is Metabolic Medicine, with a metabolic specialist / clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with metabolic specialist / clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Is a biochemical or molecular result needed to clarify the diagnosis?
• Does this condition require an individual plan for illness or reduced food intake?
• Should nutrition advice come from a specialist metabolic dietitian?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Succinyl-CoA:3-ketoacid CoA transferase deficiency. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.