Alpha-methylacyl-CoA racemase deficiency

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Alpha-methylacyl-CoA racemase (AMACR) deficiency is a disorder that causes a variety of neurological problems that begin in adulthood and slowly get worse. People with AMACR deficiency may have a gradual loss in intellectual functioning (cognitive decline), seizures, and migraines. They may also have acute episodes of brain dysfunction (encephalopathy) similar to stroke, involving altered consciousness and areas of damage (lesions) in the brain. Other features of AMACR deficiency may include weakness and loss of sensation in the limbs due to nerve damage (sensorimotor neuropathy), muscle stiffness (spasticity), and difficulty coordinating movements (ataxia). Vision problems caused by deterioration of the light-sensitive layer at the back of the eye (the retina) can also occur in this disorder.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

AMACR deficiency is caused by mutations in the AMACR gene. This gene provides instructions for making an enzyme called alpha-methylacyl-CoA racemase (AMACR).

The AMACR enzyme is found in the energy-producing centers in cells (mitochondria) and in cell structures called peroxisomes. Peroxisomes contain a variety of enzymes that break down many different substances, including fatty acids and certain toxic compounds. They are also important for the production (synthesis) of fats (lipids) used in digestion and in the nervous system. In peroxisomes, the AMACR enzyme plays a role in the breakdown of a fatty acid called pristanic acid, which comes from meat and dairy foods in the diet. In mitochondria, AMACR is thought to help further break down the molecules derived from pristanic acid.

Most individuals with AMACR deficiency have an AMACR gene mutation that results in a lack (deficiency) of functional enzyme. The enzyme deficiency leads to accumulation of pristanic acid in the blood. However, it is unclear how this accumulation is related to the specific signs and symptoms of AMACR deficiency.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

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.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

AMACR deficiency is a rare disorder. Its prevalence is unknown. At least 10 cases have been described in the medical literature.

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.

Abnormal enzyme/coenzyme activity · Very frequent (99-80%)

Concentration or activity of an enzyme is above or below the limits of normal in the blood circulation.

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.

Pigmentary retinopathy · Frequent (79-30%)

An abnormality of the retina characterized by pigment deposition. It is typically associated with migration and proliferation of macrophages or retinal pigment epithelial cells into the retina; melanin from these cells causes the pigmentary changes. Pigmentary retinopathy is a common final pathway of many retinal conditions and is often associated with visual loss.

Seizure · Frequent (79-30%)

A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

Specific learning disability · Frequent (79-30%)

Impairment of certain skills such as reading or writing, coordination, self-control, or attention that interfere with the ability to learn. The impairment is not related to a global deficiency of intelligence.

Sensorimotor neuropathy · Frequent (79-30%)

Ataxia · Occasional (29-5%)

Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).

Cataract · Occasional (29-5%)

A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule.

Cholelithiasis · Occasional (29-5%)

Hard, pebble-like deposits that form within the gallbladder.

Depression · Occasional (29-5%)

Frequently experiencing feelings of being down, miserable, and/or hopeless; struggling to recover from these moods; having a pessimistic outlook on the future; feeling a pervasive sense of shame; having a low self-worth; experiencing thoughts of suicide and engaging in suicidal behavior.

Elevated circulating creatine kinase concentration · Occasional (29-5%)

The activity of creatine kinase in the blood circulation is above the upper limit of normal.

Elevated circulating hepatic transaminase concentration · Occasional (29-5%)

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.

Giant cell hepatitis · Occasional (29-5%)

Chronic hepatitis characterized by parenchymal inflammation with formation of large multinucleated hepatocytes in response to a variety of insults to the liver.

Hematochezia · Occasional (29-5%)

The passage of fresh (red) blood per anus, usually in or with stools. Most rectal bleeding comes from the colon, rectum, or anus.

Other findings in the same source

From: Orphanet

Additional reported features include Hypogonadism (Occasional (29-5%)); Low levels of vitamin K (Occasional (29-5%)); Memory impairment (Occasional (29-5%)); Mental deterioration (Occasional (29-5%)); Migraine (Occasional (29-5%)); Rhabdomyolysis (Occasional (29-5%)); Schizophrenia (Occasional (29-5%)); Sensory neuropathy (Occasional (29-5%)); Stroke-like episode (Occasional (29-5%)); Tremor (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Alpha-methylacyl-CoA racemase deficiency is Hepatology, with a hepatologist / gastroenterologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

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.

• What is known about the cause and extent of liver involvement?
• Which medicines, supplements or exposures should be reviewed?
• What follow-up is appropriate for the specific diagnosis and stage?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Alpha-methylacyl-CoA racemase 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.