Monoamine oxidase A deficiency

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Monoamine oxidase A deficiency is a rare disorder that occurs almost exclusively in males. It is characterized by mild intellectual disability and behavioral problems beginning in early childhood.

Most boys with monoamine oxidase A deficiency are less able to control their impulses than their peers, causing aggressive or violent outbursts. In addition, affected individuals may have features of other neurodevelopmental disorders, including autism spectrum disorder and attention-deficit/hyperactivity disorder (ADHD). These features can include obsessive behaviors, difficulty forming friendships, and problems focusing attention. Sleep problems, such as trouble falling asleep or night terrors, can also occur in monoamine oxidase A deficiency.

Some people with monoamine oxidase A deficiency have episodes of skin flushing, sweating, headaches, or diarrhea. Similar episodes can occur in female family members of males with monoamine oxidase A deficiency, although females do not experience other signs or symptoms of the condition.

In some cases, certain foods, such as cheese, appear to worsen symptoms of monoamine oxidase A deficiency.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Monoamine oxidase A deficiency is caused by mutations in the MAOA gene. This gene provides instructions for making an enzyme called monoamine oxidase A. This enzyme breaks down chemicals called monoamines, including serotonin, epinephrine, and norepinephrine. These particular monoamines act as neurotransmitters, which transmit signals between nerve cells in the brain. Monoamine oxidase A helps break down the neurotransmitters when signaling is no longer needed. Signals transmitted by serotonin regulate mood, emotion, sleep, and appetite. Epinephrine and norepinephrine control the body's response to stress. Monoamine oxidase A also helps break down monoamines found in the diet.

Mutations in the MAOA gene reduce monoamine oxidase A activity, which causes serotonin and other neurotransmitters to build up in the brain. It is unclear how this buildup leads to the signs and symptoms of monoamine oxidase A deficiency. Researchers suspect that high levels of serotonin may impair an affected individual's ability to control his impulses, leading to aggressive outbursts. In addition, the outbursts may be an overreaction to stress, possibly due to the impaired breakdown of epinephrine and norepinephrine.

A reduction of monoamine oxidase A activity also impairs breakdown of monoamines found in foods. An excess of these molecules can contribute to the behavioral problems, flushing, sweating, and other symptoms associated with monoamine oxidase A deficiency, which may be why foods high in monoamines sometimes worsen the symptoms of the condition.

Monoamine oxidase A plays a role in normal brain development. Some studies suggest that reduced monoamine oxidase A activity alters the development of certain regions of the brain, which may contribute to intellectual disability and behavioral problems in people with monoamine oxidase A deficiency.

Research suggests that environmental factors, such as mistreatment in childhood, may impact the severity of the condition and the behavioral problems that develop.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Monoamine oxidase A deficiency is thought to be very rare. Its prevalence is unknown.

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.

Atypical behavior · Very frequent (99-80%)

Atypical behavior is an abnormality in a person's actions that can be controlled or modulated by the will of the individual. While abnormal behaviors can be difficult to control, they are distinct from other abnormal actions that cannot be affected by the individual's will.

Cognitive impairment · Very frequent (99-80%)

Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering.

Which doctor should you see?

The suggested department for discussing Monoamine oxidase A 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 Monoamine oxidase A 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.