X-linked adrenoleukodystrophy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

X-linked adrenoleukodystrophy is a genetic disorder that mainly affects the nervous system and the adrenal glands, which are located on top of each kidney. In this disorder, the fatty covering (myelin) that insulates nerves in the brain and spinal cord tends to deteriorate (a condition called demyelination). The loss of myelin reduces the ability of the nerves to relay information to the brain. In addition, damage to the outer layer of the adrenal glands (adrenal cortex) causes a shortage of certain hormones (adrenocortical insufficiency). Adrenocortical insufficiency may cause weakness, weight loss, skin changes, vomiting, and coma.

There are four distinct types of X-linked adrenoleukodystrophy: a childhood cerebral form, an adrenomyeloneuropathy type, an adrenal insufficiency only form, and a type called asymptomatic.

The childhood cerebral form of X-linked adrenoleukodystrophy typically occurs in boys. Girls are rarely affected with this type. If not treated, affected boys experience learning and behavioral problems that usually begin between the ages of 4 and 10. Over time the symptoms can worsen, and children may have difficulty reading, writing, understanding speech, and comprehending written material. Additional signs and symptoms of the cerebral form include aggressive behavior, vision problems, difficulty swallowing, poor coordination, and impaired adrenal gland function. The rate at which this disorder progresses is variable but can be extremely rapid, often leading to total disability within a few years. The life expectancy of individuals with this type depends on whether early diagnosis and treatment are available. Without treatment, individuals with the cerebral form of X-linked adrenoleukodystrophy usually survive only a few years after symptoms begin.

Signs and symptoms of the adrenomyeloneuropathy type appear between early adulthood and middle age. Affected individuals develop progressive stiffness and weakness in their legs (paraparesis), experience urinary and genital tract disorders, and often show changes in behavior and intellectual function. Most people with the adrenomyeloneuropathy type also have adrenocortical insufficiency. Some severely affected individuals develop cerebral X-linked adrenoleukodystrophy.

People with X-linked adrenoleukodystrophy whose only symptom is adrenocortical insufficiency are said to have the adrenal insufficiency only form. In these individuals, adrenocortical insufficiency can begin anytime between the first year of life and adulthood. However, most affected individuals develop the additional features of cerebral X-linked adrenoleukodystrophy in childhood or the adrenomyeloneuropathy type by the time they reach middle age. The life expectancy of individuals with the adrenal insufficiency form depends on the severity of the signs and symptoms, but typically this is the mildest of the three types.

Children with the asymptomatic form do not appear to have any symptoms of X-linked adrenoleukodystrophy, but medical testing may show brain or biochemical abnormalities. Some individuals with the asymptomatic form may develop features of other types of X-linked adrenoleukodystrophy later in life.

Rarely, individuals with X-linked adrenoleukodystrophy develop multiple features of the disorder in adolescence or early adulthood. In addition to adrenocortical insufficiency, these individuals usually have psychiatric disorders and a loss of intellectual function (dementia). It is unclear whether these individuals have a distinct form of the condition or a variation of one of the previously described types.

For reasons that are unclear, different forms of X-linked adrenoleukodystrophy can be seen in affected individuals within the same family.

ORPHANET DEFINITION A rare progressive peroxisomal disorder characterized by endocrine dysfunction (adrenal failure and sometimes testicular insufficiency), progressive myelopathy, peripheral neuropathy and, variably, progressive leukodystrophy.

Frequency in the source

From: MedlinePlus Genetics, National Library of Medicine

Point prevalence: 1-9 / 1 000 000; Norway; Value and class. Prevalence at birth: 1-5 / 10 000; United States; Value and class. Prevalence at birth: 1-9 / 1 000 000; Israel; Value and class.

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.

Abnormality of vision · Very frequent (99-80%)

Abnormality of eyesight (visual perception).

Attention deficit hyperactivity disorder · Very frequent (99-80%)

Attention deficit hyperactivity disorder (ADHD) manifests at age 2-3 years or by first grade at the latest. The main symptoms are distractibility, impulsivity, hyperactivity, and often trouble organizing tasks and projects, difficulty going to sleep, and social problems from being aggressive, loud, or impatient.

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.

Clumsiness · Very frequent (99-80%)

Lack of physical coordination resulting in an abnormal tendency to drop items or bump into objects.

Cognitive impairment · Very frequent (99-80%)

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

Dementia · Very frequent (99-80%)

A loss of global cognitive ability of sufficient amount to interfere with normal social or occupational function. Dementia represents a loss of previously present cognitive abilities, generally in adults, and can affect memory, thinking, language, judgment, and behavior.

Gait disturbance · Very frequent (99-80%)

The term gait disturbance can refer to any disruption of the ability to walk.

Headache · Very frequent (99-80%)

Cephalgia, or pain sensed in various parts of the head, not confined to the area of distribution of any nerve.

Other findings in the same source

From: Orphanet

Additional reported features include Hyperactivity (Very frequent (99-80%)); Incoordination (Very frequent (99-80%)); Intellectual disability (Very frequent (99-80%)); Paraparesis (Very frequent (99-80%)); Progressive hearing impairment (Very frequent (99-80%)); Somatic sensory dysfunction (Very frequent (99-80%)); Specific learning disability (Very frequent (99-80%)); Visual impairment (Very frequent (99-80%)); Visual loss (Very frequent (99-80%)); Abnormality of metabolism/homeostasis (Very frequent (99-80%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

Adolescent; Adult; Childhood; Elderly

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

X-linked

Frequency and the population described

From: MedlinePlus Genetics, National Library of Medicine

Point prevalence: 1-9 / 1 000 000; Norway; Value and class. Prevalence at birth: 1-5 / 10 000; United States; Value and class. Prevalence at birth: 1-9 / 1 000 000; Israel; Value and class.

Which doctor should you see?

The suggested department for discussing X-linked adrenoleukodystrophy 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.