Frequency
The prevalence of X-linked adrenoleukodystrophy is 1 in 15,000 individuals worldwide. This condition occurs with a similar frequency in all populations.
Causes
Variants (also known as mutations) in the ABCD1 gene cause X-linked adrenoleukodystrophy. The ABCD1 gene provides instructions for producing the adrenoleukodystrophy protein (ALDP), which is involved in transporting certain fat molecules called very long-chain fatty acids (VLCFAs) into peroxisomes. Peroxisomes are small sacs within cells that process many types of molecules, including VLCFAs.
ABCD1 gene variants result in a shortage (deficiency) of ALDP. When this protein is lacking, the transport and subsequent breakdown of VLCFAs is disrupted, causing abnormally high levels of these fats in the body. The accumulation of VLCFAs may be toxic to the adrenal cortex and myelin. Research suggests that the accumulation of VLCFAs triggers an inflammatory response in the brain, which could lead to the breakdown of myelin. The destruction of these tissues leads to the signs and symptoms of X-linked adrenoleukodystrophy.
Inheritance
X-linked adrenoleukodystrophy is inherited in an X-linked pattern. A condition is considered X-linked if the altered gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In males (who have only one X chromosome), one altered copy of the ABCD1 gene in each cell is sufficient to cause X-linked adrenoleukodystrophy. Additionally, affected males pass the altered gene to all of their daughters but none of their sons.
Because females have two copies of the X chromosome, one altered copy of the ABCD1 gene in each cell usually does not cause features of X-linked adrenoleukodystrophy that are as severe as those in affected males. Most affected females with one altered copy of the gene develop features of the adrenomyeloneuropathy type. The signs and symptoms of X-linked adrenoleukodystrophy tend to appear at a later age in affected females than in affected males. Additionally, affected females have a 50 percent chance of passing the altered gene to each of their children.
Other Names for This Condition
- X-ALD
Additional Information & Resources
Genetic Testing Information
Genetic and Rare Diseases Information Center
Patient Support and Advocacy Resources
Clinical Trials
Catalog of Genes and Diseases from OMIM
Scientific Articles on PubMed
References
- Berger J, Gartner J. X-linked adrenoleukodystrophy: clinical, biochemical and pathogenetic aspects. Biochim Biophys Acta. 2006 Dec;1763(12):1721-32. doi: 10.1016/j.bbamcr.2006.07.010. Epub 2006 Jul 26. Citation on PubMed
- Dubey P, Raymond GV, Moser AB, Kharkar S, Bezman L, Moser HW. Adrenal insufficiency in asymptomatic adrenoleukodystrophy patients identified by very long-chain fatty acid screening. J Pediatr. 2005 Apr;146(4):528-32. doi: 10.1016/j.jpeds.2004.10.067. Citation on PubMed
- Engelen M, Kemp S, de Visser M, van Geel BM, Wanders RJ, Aubourg P, Poll-The BT. X-linked adrenoleukodystrophy (X-ALD): clinical presentation and guidelines for diagnosis, follow-up and management. Orphanet J Rare Dis. 2012 Aug 13;7:51. doi: 10.1186/1750-1172-7-51. Citation on PubMed or Free article on PubMed Central
- Kemp S, Berger J, Aubourg P. X-linked adrenoleukodystrophy: clinical, metabolic, genetic and pathophysiological aspects. Biochim Biophys Acta. 2012 Sep;1822(9):1465-74. doi: 10.1016/j.bbadis.2012.03.012. Epub 2012 Mar 28. Citation on PubMed
- Kemp S, Pujol A, Waterham HR, van Geel BM, Boehm CD, Raymond GV, Cutting GR, Wanders RJ, Moser HW. ABCD1 mutations and the X-linked adrenoleukodystrophy mutation database: role in diagnosis and clinical correlations. Hum Mutat. 2001 Dec;18(6):499-515. doi: 10.1002/humu.1227. Citation on PubMed
- Moser HW, Mahmood A, Raymond GV. X-linked adrenoleukodystrophy. Nat Clin Pract Neurol. 2007 Mar;3(3):140-51. doi: 10.1038/ncpneuro0421. Citation on PubMed
- Moser HW, Raymond GV, Lu SE, Muenz LR, Moser AB, Xu J, Jones RO, Loes DJ, Melhem ER, Dubey P, Bezman L, Brereton NH, Odone A. Follow-up of 89 asymptomatic patients with adrenoleukodystrophy treated with Lorenzo's oil. Arch Neurol. 2005 Jul;62(7):1073-80. doi: 10.1001/archneur.62.7.1073. Citation on PubMed
- Tran C, Patel J, Stacy H, Mamak EG, Faghfoury H, Raiman J, Clarke JTR, Blaser S, Mercimek-Mahmutoglu S. Long-term outcome of patients with X-linked adrenoleukodystrophy: A retrospective cohort study. Eur J Paediatr Neurol. 2017 Jul;21(4):600-609. doi: 10.1016/j.ejpn.2017.02.006. Epub 2017 Feb 21. Citation on PubMed
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