Adrenoleukodystrophy (uh-dree-noh-loo-koh-DIS-truh-fee) is a type of hereditary (genetic) condition that damages the membrane (myelin sheath) that insulates nerve cells in your brain.
In adrenoleukodystrophy (ALD), your body can't break down very long-chain fatty acids (VLCFAs), causing saturated VLCFAs to build up in your brain, nervous system and adrenal gland.
The most common type of ALD is X-linked ALD, which is caused by a genetic defect on the X chromosome. X-linked ALD affects males more severely than females, who carry the disease.
Forms of X-linked ALD include:
- Childhood-onset ALD. This form of X-linked ALD usually occurs between ages 4 and 10. The white matter of the brain is progressively damaged (leukodystrophy), and symptoms worsen over time. If not diagnosed early, childhood-onset ALD may lead to death within five to 10 years.
- Addison's disease. Hormone-producing glands (adrenal glands) often fail to produce enough steroids (adrenal insufficiency) in people who have ALD, causing a form of X-linked ALD known as Addison's disease.
- Adrenomyeloneuropathy. This adult-onset form of X-linked ALD is a less severe and slowly progressive form that causes symptoms such as a stiff gait and bladder and bowel dysfunction. Women who are carriers for ALD may develop a mild form of adrenomyeloneuropathy.
To diagnose ALD, your doctor will review your symptoms and your medical and family history. Your doctor will conduct a physical examination and order several tests, including:
Blood testing. These tests check for high levels of very long-chain fatty acids (VLCFAs) in your blood, which are a key indicator of adrenoleukodystrophy.
Doctors use blood samples for genetic testing to identify defects or mutations that cause ALD. Doctors also use blood tests to evaluate how well your adrenal glands work.
- MRI. Powerful magnets and radio waves create detailed images of your brain in an MRI scan. This allows doctors to detect abnormalities in your brain that could indicate adrenoleukodystrophy, including damage to the nerve tissue (white matter) of your brain. Doctors may use several types of MRI to view the most-detailed images of your brain and detect early signs of leukodystrophy.
- Vision screening. Measuring visual responses can monitor disease progression in males who have no other symptoms.
- Skin biopsy and fibroblast cell culture. A small sample of skin may be taken to check for increased levels of VLCFA in some cases.
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