X-linked Adrenoleukodystrophy

Definition

X-linked adrenoleukodystrophy (ALD) is a rare inherited genetic disorder. There are 40 subtypes of leukodytsrophy. X-linked ALD is the most common category. ALD results in degeneration of the:

  • Myelin sheath— the fatty insulation covering on nerve fibers in the brain
  • Adrenal gland and surrounding adrenal cortex—produces vital hormones
Myelin Sheath Around Nerve Fiber
AX00010 97870 1 myelin sheath
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There are six subtypes of X-linked ALD:

  • Childhood cerebral ALD
  • Adolescent ALD
  • Adrenomyeloneuropathy
  • Adult cerebral ALD
  • Adrenal insufficiency-only
  • Symptomatic heterozygotes

Causes

ALD is caused by an inherited defective gene.

In people with ALD, the body cannot properly break down fatty acids. This results in a build up of saturated fatty acids in the brain and the adrenal cortex. This causes damage of the myelin sheath in the brain and the adrenal gland.

Risk Factors

This condition is most common in males, although females may also be affected. It is also more common in children and young adults. Having a mother who carries the defective X-linked ALD gene may increase your risk.

Symptoms

Symptoms can vary within the types of ALD.

X-linked ALD (Childhood Cerebral ALD)

This form is the most severe. It only affects boys. Symptoms usually begin between 2–10 years of age. About 35% of patients can have severe symptoms during the early phase. On average, death results in two years. Some patients may live a couple of decades.

Initial symptoms include:

  • Behavioral changes
  • Poor memory
  • A slowing down of thought processes and physical activity
  • Developmental regression

As the disease progresses, more serious symptoms develop. These include:

  • Vision loss
  • Seizures
  • Hearing loss
  • Difficulty swallowing and speaking
  • Difficulty with walking and coordination
  • Vomiting
  • Fatigue
  • Increased pigmentation of the skin, due to adrenal hormone deficiency— Addison’s disease
  • Progressive dementia
  • Vegetative state or death

X-linked ALD (Adolescent Cerebral ALD)

This type is similar to the childhood type. It begins around 11-21 years of age. The progression is usually slower.

Adrenomyeloneuropathy (AMN)

This is the most common form. Symptoms of AMN can present in the 20s. It progresses slowly. They can include:

  • Weakness, clumsiness, weight loss, nausea
  • Emotional disturbances or depression
  • Motor/movement problems, such as walking problems
  • Urinary problems or impotence

X-linked ALD (Adult Cerebral ALD)

With this type, symptoms usually do not appear until young adulthood (20s) or middle age (50s). It causes symptoms similar to schizophrenia and dementia . It usually progresses quickly. Death or a vegetative state can occur in 3-4 years.

Symptomatic Heterozygotes

This form is only seen in women. Symptoms may be mild or severe. It usually does not affect the adrenal gland function.

Diagnosis

You will be asked about your symptoms and medical history. A physical exam will be done.

Your bodily fluids may be tested. This can be done with:

  • Blood tests
  • Genetic testing

Images may be taken of your brain. This can be done with an MRI scan .

Treatment

There is no known cure for the brain damage of ALD. However, the adrenal deficiency can be treated with cortisone replacement. ALD often causes death within 10 years of the onset of symptoms.

Some therapies can help manage the symptoms of ALD. These include:

  • Physical therapy
  • Psychological therapy
  • Special education for children

There are also some experimental treatments. Some treatments that are still being investigated that you may want to talk to your doctor about include:

  • Bone marrow transplantation —this procedure may be most helpful when given early to boys with X-linked child-onset ALD
  • Dietary therapy, which includes consumption of:
    • A low fat diet
    • Lorenzo’s oil—dietary supplements of glycerol trioleate and glycerol trierucate
  • Lovastatin—an anti-cholesterol medication
  • Medications that affect interactions between DNA and other proteins

Prevention

There is no known way to prevent ALD. If you have ALD or have a family history of the disorder, you can talk to a genetic counselor when deciding to have children.

Early recognition and treatment may prevent symptoms from developing. New technologies may soon allow early identification through newborn screening.

Revisions

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