X-linked adrenoleukodystrophy (X-ALD) is a genetic condition that affects how your body breaks down certain fats called very long-chain fatty acids (VLCFAs). Imagine your cells have tiny recycling centers (called peroxisomes) that process these fats. X-ALD happens when a specific gene, the ABCD1 gene, has a change (a mutation) that makes it hard for these recycling centers to work properly. This causes VLCFAs to build up, which can be harmful, especially to your brain, spinal cord, and adrenal glands.
How is X-ALD passed on?
Typically, X-ALD is passed down through families and the gene (ABCD1) is located on the X chromosome, one of the two chromosomes that determine your sex. Males have one X and one Y chromosome, while females have two X chromosomes. Because of this, X-ALD affects males and females differently.
- Genetic males: Males only have one X chromosome. If that one X chromosome has the changed (“mutated”) ABCD1 gene, they will likely develop X-ALD.
- Genetic females: Females have two X chromosomes. If a person has one X chromosome with the changed ABCD1 gene and the other one with a normal ABCD1 gene, they are called “carriers.” Many female carriers don’t experience any symptoms or only have mild ones. However, some female carriers can develop symptoms later in life.
About 90% of the time, X-ALD is inherited from a parent. In some cases, the gene change occurs for the first time in a person, which is called a de novo mutation. Because some female carriers have normal VLCFA levels in their blood, genetic testing is the most reliable way to know if a woman carries a change in the ABCD1 gene鈥攅specially if a family member has X-ALD.
How does X-ALD affect people with two X chromosomes? The adrenomyeloneuropathy (AMN) story.
While some XX women who carry the X-ALD gene change don’t experience any problems, many develop symptoms, usually after the age of 30. By age 60, over 80% of XX genetic females with one changed ABCD1 gene have symptoms. How severe symptoms are also varies a lot person to person.
Most woman with X-ALD related symptoms experience something called X-ALD related adrenomyeloneuropathy (AMN) syndrome.
Adrenal gland problems are rare but possible in women with AMN. Adrenal gland problems can lead to sleepiness, muscle weakness, weight loss, and other symptoms.
AMN affects the spinal cord (myelopathy) and peripheral nerves (neuropathy). AMN can cause numbness, stiff legs, weakness, trouble walking, joint pain, and other neurological problems such as urinary problems.
X-ALD related AMN syndromes may impact just one area, so people may hear more specific diagnoses like “X-ALD related myelopathy” instead of AMN or AMN syndrome.
Changes in the brain are very rare.
Why is it important to know about X-ALD and related AMN?
Because symptoms can vary and often don’t appear until later in life, it’s important for women who might be carriers to be aware of the possibility of X-ALD related disorders, especially AMN. Early recognition of symptoms can help with getting the right care and improving outcomes.
How is X-ALD diagnosed?
In some states, including North Carolina, X-ALD is part of newborn screening. If a baby is diagnosed with X-ALD, the mother can be tested to see if she is a carrier. If a woman is a carrier, she should see a neurologist and genetic counselor for ongoing care and to discuss the implications for her health and for future children.
How is AMN diagnosed?
Genetic testing is the best way to diagnose AMN in women.
VLCFA levels are often normal in XX ALD carriers, so measuring VLCFA levels in usually not part of AMN diagnosis.
Tests of peripheral nerves, like an EMG and nerve conduction study, may be used.
Spinal cord changes in X-ALD syndromes are often not detected on imaging, so studies like spine MRI’s are generally not useful in AMN diagnosis.
How is AMN managed?
Care for women with AMN is personalized and focuses on managing symptoms. A team of specialists may be involved, including:
- Neurologists: They will monitor and treat any nerve-related problems.
- Endocrinologists: They will check for and manage any (rare) adrenal gland issues.
- Physical therapists: They can help with mobility and muscle weakness.
- Genetic counselors: They can explain the condition, discuss the chances of it being passed on to children, and talk about family planning options.
Where can I find support?
There are many organizations that offer support and information for people with X-ALD and their families:
- Adrenoleukodystrophy (ALD) Foundation: aldfoundation.org
- ALD Connect and the Myelin Project: aldconnect.org/women/
- X-ALD Support Network: x-aldsupport.org
- The Leukodystrophy Care Network: leukodystrophycare.org
- ALD Information Network: adrenoleukodystrophy.info
- Adrenoleukodystrophy News:
These resources can provide valuable information, connect you with other families affected by X-ALD, and offer support.