Adrenoleukodystrophy (ALD) is one of a group of genetic disorders called the leukodystrophies that cause damage to the myelin sheath, an insulating membrane that surrounds nerve cells in the brain. People with ALD accumulate high levels of saturated, very long chain fatty acids (VLCFA) in the brain and adrenal cortex because they do not produce the enzyme that breaks down these fatty acids in the normal manner. The loss of myelin and the progressive dysfunction of the adrenal gland are the primary characteristics of ALD.
ALD has two subtypes. The most common is the X-linked form (X-ALD), which involves an abnormal gene located on the X-chromosome. Women have two X-chromosomes and are the carriers of the disease, but since men only have one X-chromosome and lack the protective effect of the extra X-chromosome, they are more severely affected. Onset of X-ALD can occur in childhood or in adulthood.
The childhood form is the most severe, with onset between ages 4 and 10. The most common symptoms are usually behavioral changes such as abnormal withdrawal or aggression, poor memory, and poor school performance. Other symptoms include:
In the milder adult-onset form, which typically begins between ages 21 and 35, symptoms may include:
Although adult-onset ALD progresses more slowly than the classic childhood form, it can also result in deterioration of brain function.
A mild form of ALD is occasionally seen in women who are carriers of the disorder. Symptoms include:
Adrenal function must be tested periodically in all patients with ALD. Treatment with adrenal hormones can be lifesaving. Symptomatic and supportive treatments for ALD include physical therapy, psychological support, and special education. Recent evidence suggests that a mixture of oleic acid and erucic acid, known as "Lorenzo's Oil," administered to boys with X-ALD can reduce or delay the appearance of symptoms. Bone marrow transplants can provide long-term benefit to boys who have early evidence of X-ALD, but the procedure carries risk of mortality and morbidity and is not recommended for those whose symptoms are already severe or who have the adult-onset or neonatal forms. Oral administration of docosahexanoic acid (DHA) may help infants and children with neonatal ALD.
Prognosis for patients with ALD is generally poor due to progressive neurological deterioration. Death usually occurs within 1 to 10 years after the onset of symptoms.