Ornithine transcarbamylase deficiency

What it is

From: Orphanet

A rare, genetic disorder of urea cycle metabolism and ammonia detoxification characterized by either a severe, neonatal-onset disease found mainly in males, or later-onset (partial) forms of the disease. Both present with episodes of hyperammonemia that can be fatal and which can lead to neurological sequelae.

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.

Aminoaciduria · Very frequent (99-80%)

An increased concentration of an amino acid in the urine.

Hyperammonemia · Very frequent (99-80%)

An increased concentration of ammonia in the blood.

Hypoglycemia · Very frequent (99-80%)

A decreased concentration of glucose in the blood.

Splenomegaly · Very frequent (99-80%)

Abnormal increased size of the spleen.

Hepatic failure · Very frequent (99-80%)

Anorexia · Frequent (79-30%)

Lack of desire to eat (loss of appetite).

Coma · Frequent (79-30%)

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

Drowsiness · Frequent (79-30%)

Abnormal feeling of sleepiness or difficulty staying awake.

Elevated circulating hepatic transaminase concentration · Frequent (79-30%)

Elevations of the levels of SGOT and SGPT in the serum. SGOT (serum glutamic oxaloacetic transaminase) and SGPT (serum glutamic pyruvic transaminase) are transaminases primarily found in the liver and heart and are released into the bloodstream as the result of liver or heart damage. SGOT and SGPT are used clinically mainly as markers of liver damage.

Encephalopathy · Frequent (79-30%)

Encephalopathy is a term that means brain disease, damage, or malfunction. In general, encephalopathy is manifested by an altered mental state.

Hypoargininemia · Frequent (79-30%)

The concentration of arginine in the blood circulation is below the lower limit of normal.

Hypothermia · Frequent (79-30%)

Reduced body temperature due to failed thermoregulation.

Hypotonia · Frequent (79-30%)

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 · Frequent (79-30%)

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.

Other findings in the same source

From: Orphanet

Additional reported features include Low plasma citrulline (Frequent (79-30%)); Oroticaciduria (Frequent (79-30%)); Poor suck (Frequent (79-30%)); Respiratory alkalosis (Frequent (79-30%)); Seizure (Frequent (79-30%)); Protein avoidance (Frequent (79-30%)); Anxiety (Occasional (29-5%)); Attention deficit hyperactivity disorder (Occasional (29-5%)); Delirium (Occasional (29-5%)); Depression (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

All ages

Inheritance in the source

From: Orphanet

X-linked recessive

Frequency and the population described

From: Orphanet

Point prevalence: 1-9 / 100 000; Europe; Value and class. Prevalence at birth: 1-9 / 100 000; Italy; Value and class. Prevalence at birth: 1-9 / 100 000; Australia; Value and class. Prevalence at birth: 1-9 / 100 000; Finland; Value and class.

Understanding the inheritance label

From: MedlinePlus Genetics

An X-linked recessive pattern involves a gene on the X chromosome. The number of X chromosomes and the particular genetic change influence how a condition is expressed. A genetic counsellor should interpret the result and the family history before discussing risks for relatives or future pregnancies.

Which doctor should you see?

The suggested department for discussing Ornithine transcarbamylase 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 Ornithine transcarbamylase 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.