Cerebrotendinous xanthomatosis

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Cerebrotendinous xanthomatosis is a disorder characterized by abnormal storage of fats (lipids) in many areas of the body. People with this disorder cannot break down certain lipids effectively, specifically different forms of cholesterol, so these fats accumulate in the body in the form of fatty yellow nodules called xanthomas. These xanthomas are most commonly found in the brain and in connective tissue called tendons that attach muscle to bone, which is reflected in the condition name (cerebro- meaning brain and -tendinous referring to tendons).

People with cerebrotendinous xanthomatosis often develop neurological problems in early adulthood that are thought to be caused by an abnormal accumulation of fats and an increasing number of xanthomas in the brain. These neurological problems include recurrent seizures (epilepsy), movement disorders, impaired speech (dysarthria), loss of sensation in the arms and legs (peripheral neuropathy), decline in intellectual function (dementia), hallucinations, and depression. Xanthomas can accumulate in the fatty substance that insulates and protects nerves (myelin), causing the destruction of myelin and disrupting nerve signaling in the brain. Degeneration (atrophy) of brain tissue caused by excess lipid deposits also contributes to the neurological problems.

Xanthomas in the tendons begin to form in early adulthood. The most common areas for xanthomas to develop are tendons in the hands, elbows, knees, neck, and in the Achilles tendon, which connects the heel of the foot to the calf muscles in the leg. Tendon xanthomas may cause discomfort and interfere with tendon flexibility. While many affected people develop tendon xanthomas, these nodules may not be easily visible underneath the skin.

Other features of cerebrotendinous xanthomatosis include clouding of the lenses of the eyes (cataracts) and chronic diarrhea in childhood; a reduced ability to produce and release a digestive fluid called bile (cholestasis), which can lead to a yellowing of the skin or whites of the eyes (jaundice); and progressively brittle bones that are prone to fracture (osteoporosis). People with cerebrotendinous xanthomatosis are also at an increased risk of developing cardiovascular disease or respiratory failure because of lipid accumulation in the heart or lungs, respectively. If untreated, the signs and symptoms related to cerebrotendinous xanthomatosis worsen over time; however, this condition varies greatly among those who are affected.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the CYP27A1 gene cause cerebrotendinous xanthomatosis. The CYP27A1 gene provides instructions for producing an enzyme called sterol 27-hydroxylase. This enzyme works in the pathway that breaks down cholesterol to form acids used in the digestion of fats (bile acids), specifically a bile acid called chenodeoxycholic acid.

Mutations in the CYP27A1 gene lead to the production of a nonfunction or abnormal sterol 27-hydroxylase that cannot help form chenodeoxycholic acid. As a result, other molecules are formed by an alternative pathway. A molecule called cholestanol, which is similar to cholesterol, is produced as well as substances called bile alcohols. Cholestanol and bile alcohols are increased in the blood, while blood cholesterol levels are typically normal. In various tissues in the body, including the brain and heart, cholesterol and cholestanol levels are increased. These lipids make up much of the fats found in xanthomas. The accumulation of cholesterol and cholestanol throughout the body's tissues causes the signs and symptoms of cerebrotendinous xanthomatosis.

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

The incidence of cerebrotendinous xanthomatosis is estimated to be 1 per million individuals worldwide. This condition is more common in the Moroccan Jewish population with an incidence of 1 in 108 individuals.

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.

Juvenile cataract · Very frequent (99-80%)

A type of cataract that is not apparent at birth but that arises in childhood or adolescence.

Visual impairment · Very frequent (99-80%)

Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery.

Abnormal auditory evoked potentials · Frequent (79-30%)

An abnormality of the auditory evoked potentials, which are used to trace the signal generated by a sound, from the cochlear nerve, through the lateral lemniscus, to the medial geniculate nucleus, and to the cortex.

Abnormal cerebellum morphology · Frequent (79-30%)

Any structural abnormality of the cerebellum.

Abnormal globus pallidus morphology · Frequent (79-30%)

An abnormality of the globus pallidus.

Abnormal motor evoked potentials · Frequent (79-30%)

An anomaly identified by motor evoked potentials (MEPs). MEPs are measured following single-pulse or repetitive transcranial magnetic stimulation and can be used for the assessment of the excitability of the motor cortex and the integrity of conduction along the central and peripheral motor pathways.

Abnormal pyramidal sign · Frequent (79-30%)

Functional neurological abnormalities related to dysfunction of the pyramidal tract.

Other findings in the same source

From: Orphanet

Additional reported features include Abnormal retinal vascular morphology (Frequent (79-30%)); Abnormality of extrapyramidal motor function (Frequent (79-30%)); Abnormality of finger (Frequent (79-30%)); Abnormality of somatosensory evoked potentials (Frequent (79-30%)); Abnormality of the Achilles tendon (Frequent (79-30%)); Abnormality of the cerebellar peduncle (Frequent (79-30%)); Abnormality of the plantar skin of foot (Frequent (79-30%)); Abnormality of tibia morphology (Frequent (79-30%)); Abnormality of visual evoked potentials (Frequent (79-30%)); Ataxia (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Cerebrotendinous xanthomatosis 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

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

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.