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Adrenoleukodystrophy (ALD)

Frank Gaillard

Adrenoleukodystrophy is a rare genetic disorder in which the myelin sheath becomes damaged. Due to this damage, termed as demyelination, the nerves are unable to function as well as they should. Features in this MRI scan are consistent with X-linked adrenoleukodystrophy.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Addison Disease with Cerebral Sclerosis
  • Adrenomyeloneuropathy (AMN)
  • ALD (Adrenoleukodystrophy)

What is Adrenoleukodystrophy? (Definition/Background Information)

  • Adrenoleukodystrophy (ALD) is a rare genetic disorder in which the myelin sheath (membrane covering the nerve cells in the brain), becomes damaged. Due to this damage, termed as demyelination, the nerves are unable to function as well as they should
  • Individuals with ALD are unable to produce transporter proteins, which are essential in carrying enzymes that breakdown ‘long chains’ of saturated fatty acids in the body. As fatty acid chains buildup in the body, the brain and nerve function begins to deteriorate
  • With this abnormal accumulation in the brain cells and nerve cells, a variety of signs and symptoms can occur. These include vision and hearing problems, improper gait, and body balance/coordination problems
  • A diagnosis of ALD is usually made through blood tests and radio imaging studies
  • There is no cure for the condition and prognosis depends on the severity of the signs and symptoms

Who gets Adrenoleukodystrophy? (Age and Sex Distribution)

While mild forms of Adrenoleukodystrophy have been seen in carrier females, full-blown disorders with severe symptoms are seen, exclusively in males. ALD can occur at any age.

  • If the symptoms appear between the ages of 4 and 10, individuals are diagnosed with childhood cerebral form of ALD
  • It can also occur during adolescence, called adolescent cerebral ALD
  • If it occurs during early to late adulthood, they are diagnosed with a disorder known as adrenomyelopathy
  • Individuals of all race/ethnic background are prone to the condition

What are the Risk Factors for Adrenoleukodystrophy? (Predisposing Factors)

Adrenoleukodystrophy is passed down as an X-linked genetic trait and hence, a positive family history is a significant risk factor.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Adrenoleukodystrophy? (Etiology)

  • Adrenoleukodystrophy is caused by mutations on the ABCD1 gene of the X chromosome
  • When mutations occur on this gene, very long chains of fatty acids accumulate, because transporter proteins are not produced to break them down
  • These mutations also cause demyelination of nerves - the stripping away of the myelin sheath (fatty coat) of nerves in the brain. These two malfunctions, cause signs and symptoms of ALD

ALD is passed down from parents to children as an X-linked trait. This means that if a male child inherits the mutated X chromosome, they will have ALD. A female child, on the other hand, will be a carrier of the disorder, but will not be affected by it.

What are the Signs and Symptoms of Adrenoleukodystrophy?

Signs and symptoms vary depending on when Adrenoleukodystrophy is onset, in the individual.

Individuals with Childhood/Adolescent Cerebral ALD may show the following signs and symptoms:

  • Change in muscle tone
  • Crossed eyes
  • Hearing loss
  • Hyperactivity
  • Nervous system deterioration
  • Seizures
  • Difficulty swallowing
  • Vision loss
  • Coordination difficulties, difficulty in school
  • Dementia

In adults, who have adrenomyelopathy, the signs and symptoms may include:

  • Muscle weakness
  • Cognitive difficulties
  • Memory loss
  • Difficulty controlling urination
  • Limb paralysis

How is Adrenoleukodystrophy Diagnosed?

A diagnosis of Adrenoleukodystrophy would involve:

  • Physical exam, medical history study, review of the individual’s symptoms
  • Blood tests: These are done to test for high levels of very long chains of fatty acids in blood
  • Genetic test: The blood can also be used to conduct genetic tests - testing for mutations on the ABCD1 gene
  • MRI scan of brain: Performed to image the brain and determine, if there are abnormalities that indicate ALD
  • Skin biopsy: May also be done in some cases, to check for increased levels of very long chains of fatty acids

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Adrenoleukodystrophy?

Individuals suffering from Adrenoleukodystrophy may suffer severe, life-threatening complications.

  • Adrenal crisis may occur, if sufficient cortisol is not produced by the adrenal glands. Cortisol is a steroid that is produced in the adrenal glands and is essential in maintaining normal body function
  • Individuals may also go into a long-term coma, or a vegetative state, due to extensive damage to the brain cells

How is Adrenoleukodystrophy Treated?

Currently, there is no cure for Adrenoleukodystrophy. However, treatment options that can reduce the severity of symptoms and allow individuals with ALD, to live more normal lives include:

  • Having a diet that is low in long chain fatty acids and taking a variety of special oils, which have been shown to reduce the levels of very long chain fatty acids in blood. A decrease in long chain fatty acids in blood, slows down its accumulation in the brain tissue, due to which the progression of the disorder may be decreased
  • Stem cell transplants can also help reduce symptoms of ALD. If the disorder is detected early enough, stem cell and bone marrow transplants could help slow down, or even stop the progression of ALD in the body. In spite of such treatment, ALD is a progressive disorder, wherein the signs and symptoms get worse with time
  • Medications to reduce muscle stiffness and seizures may be prescribed
  • Physical therapy can help reduce muscle spasms and improve muscle strength

How can Adrenoleukodystrophy be Prevented?

  • Currently, there are no specific methods or guidelines to prevent Adrenoleukodystrophy genetic condition
  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis of Adrenoleukodystrophy? (Outcomes/Resolutions)

  • Individuals with the childhood form of Adrenoleukodystrophy degenerate quickly. They usually fall into a vegetative state, two years after the nervous system symptoms develop. These children can live in this state for around 10 years, before death occurs
  • Individuals, diagnosed with the adult form of ALD have milder symptoms, which give them a longer life expectancy and more hope for a relatively normal life

Additional and Relevant Useful Information for Adrenoleukodystrophy:

X-linked recessive: X-linked recessive conditions are traits or disorders that occur when two copies of an abnormal gene are inherited on a sex chromosome (X or Y chromosome). All X-linked recessive traits are fully evident in males, because they have only one copy of the X chromosome. This means that there is no normal gene present to mask the effects of the mutant copy. All males who are affected will pass the mutated gene onto their female offspring, because they must inherit one copy of the X chromosome from each parent. This means that they will be unaffected carriers. Females are rarely affected by X-linked recessive disorders because they have two copies of the X chromosome. In the rare case that they inherit two mutated copies of the gene, they will inherit the condition.

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

What are some Useful Resources for Additional Information?

The Adrenoleukodystrophy Foundation
241 Camden Street Slidell, LA 70461
Phone: (985) 718-4728
Email: information@aldfoundation.org
Website: http://www.aldfoundation.org

References and Information Sources used for the Article:

http://www.aldfoundation.org/ald_info.html (accessed on August 5, 2012)

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002165/ (accessed on August 5, 2012)

http://www.mayoclinic.org/adrenoleukodystrophy/ (accessed on August 6, 2012)

http://www.bbc.co.uk/health/physical_health/conditions/adrenoleukodystrophy1.shtml (accessed on August 5, 2012)

Helpful Peer-Reviewed Medical Articles:

Cappa, M., Bizzarri, C., Vollono, C., Petroni, A., &Banni, S. (2011). Adrenoleukodystrophy.Endocr Dev, 20, 149-160. doi: 10.1159/000321236

Galea, E., Launay, N., Portero-Otin, M., Ruiz, M., Pamplona, R., Aubourg, P., . . .Pujol, A. (2012). Oxidative stress underlying axonal degeneration in adrenoleukodystrophy: a paradigm for multifactorial neurodegenerative diseases? BiochimBiophysActa, 1822(9), 1475-1488. doi: 10.1016/j.bbadis.2012.02.005

Geillon, F., Trompier, D., Gondcaille, C., Lizard, G., &Savary, S. (2012). [Peroxisomal ABC transporters and X-linked adrenoleukodystrophy]. Med Sci (Paris), 28(12), 1087-1094. doi: 10.1051/medsci/20122812019

Jangouk, P., Zackowski, K. M., Naidu, S., & Raymond, G. V. (2012). Adrenoleukodystrophy in female heterozygotes: underrecognized and undertreated. Mol Genet Metab, 105(2), 180-185. doi: 10.1016/j.ymgme.2011.11.001

Kemp, S., Berger, J., &Aubourg, P. (2012). X-linked adrenoleukodystrophy: clinical, metabolic, genetic and pathophysiological aspects. BiochimBiophysActa, 1822(9), 1465-1474. doi: 10.1016/j.bbadis.2012.03.012

Shimozawa, N., Honda, A., Kajiwara, N., Kozawa, S., Nagase, T., Takemoto, Y., & Suzuki, Y. (2011). X-linked adrenoleukodystrophy: diagnostic and follow-up system in Japan. J Hum Genet, 56(2), 106-109. doi: 10.1038/jhg.2010.139

Matsukawa, T., Asheuer, M., Takahashi, Y., Goto, J., Suzuki, Y., Shimozawa, N., ... & Tsuji, S. (2011). Identification of novel SNPs of ABCD1, ABCD2, ABCD3, and ABCD4 genes in patients with X-linked adrenoleukodystrophy (ALD) based on comprehensive resequencing and association studies with ALD phenotypes. Neurogenetics, 12(1), 41-50.

Cartier, N., Hacein-Bey-Abina, S., Von, C. K., Bougnères, P., Fischer, A., Cavazzana-Calvo, M., & Aubourg, P. (2010). Gene therapy of x-linked adrenoleukodystrophy using hematopoietic stem cells and a lentiviral vector. Bulletin de l'Academie nationale de medecine, 194(2), 255-64.