Adrenoleukodystrophy (ALD) is a degenerative disorder of nerve fibers. It is a type of leukodystrophy . Leukodystrophies are dysmyelinating disorders, in which there is an abnormal myelin formation due to a metabolic disturbance affecting the white matter. They are different from demyelinating disorders such as multiple sclerosis, in which myelin is formed normally, but is lost by immunologic dysfunction or other reasons.
The most common form of ALD is X-linked (the defective gene is on the X chromosome), and is characterized by excessive accumulation of very long chain fatty acids (VLCFA) - fatty acids chains longer than 22 carbons in length. It appears to be caused by the deficiency of one or more transport proteins responsible for the import and degradation of VLCFAs into peroxisomes which are responsible for their metabolism via β-oxidation.
The precise mechanisms through which high VLCFA concentrations cause the disease are still unknown (2005).
The clinical presentations largely depend on the age of onset of the disease. The most frequent type is the childhood-onset one, which is characterized by failure to develop, seizures, ataxia, adrenal insufficiency and degeneration of visual and auditory function.
In adolescent-onset form, the spinal cord dysfunction is more prominent and therefore is called adrenomyeloneuropathy. The patients usually present with weakness and numbness of the limbs and urination or defecation problems.
Adult and neonatal forms of the disease are also present, but they are extremely rare. Some patients may present with sole findings of adrenal insufficiency (Addison's disease).
The diagnosis is established by clinical findings and the detection of serum long chain fatty acid levels. MRI examination reveals white matter abnormalities, and neuroimaging findings of this disease are quite reminiscent of the findings of multiple sclerosis. Genetic testing for the analysis of the defective gene is available in some centers.
There is no definite treatment for the disease. Some dietary treatments, e. g., Lorenzo's oil, have been used with limited success. Bone marrow transplantation may be helpful for some mild cases.
External link
http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=300100 http://www.peroxisome.org/Scientist/Biochemistry/XALD.html
Last updated: 05-08-2005 04:37:50
