Adrenomyeloneuropathy Affects Spine's Nerve Cells, and Potentially Adrenal Glands and Brain
Rare Genetic Disease
Adrenomyeloneuropathy is a rare genetic disease that is a form of adrenoleukodystrophy. The disease affects the nerve cells in the spine and possibly the brain and the adrenal glands. The first symptoms are often trouble walking.
Adrenomyeloneuropathy most often occurs in young men (20 to 40 years) but may begin anywhere between the ages of 20 and 50 years. Women may also be affected but with later and milder symptoms, or may be carriers of the disease, meaning that they do not show symptoms but can pass the genetic trait to their children.
The disease has two main types: adrenomyeloneuropathy with cerebral involvement (both the spinal cord and brain are affected), and adrenomyeloneuropathy without cerebral involvement (only the spinal cord is affected).
Adrenomyeloneuropathy is caused by a genetic defect (mutation) of the ABCD1 gene on the X chromosome that causes a buildup of a specific type of fat in the body called very-long chain fatty acids. This buildup results in damage to the myelin sheath in the brain and/or spinal cord, and possibly the adrenal gland. The myelin sheath insulates and protects nerve cells and when it breaks down, the nerves have trouble transmitting messages from or to the brain and as a result the body loses control of certain functions.
Symptoms of adrenomyeloneuropathy include the following:
- Weakness and stiffness in the legs that worsens over time
- Difficulty walking or change in walking pattern
- Trouble with muscle control
- Problems urinating
- Urinary and genital tract disorders
- Behavioral changes (when the brain is affected)
- Vision changes (when the brain is affected)
Some patients also have problems with their adrenal glands (they don’t make enough steroid hormones), which is called Addison’s disease. These patients commonly have the following symptoms:
- Marked fatigue and weakness
- Weight loss
- Darkened skin (increased pigmentation)
- Unexplained vomiting and decreased appetite
- Lightheadedness and dizziness
- Loss of consciousness, fainting
Diagnosis may be made from a simple blood test that measures the amount of very long-chain fatty acids in the blood or blood cells. Magnetic resonance imaging (MRI) of the brain, genetic testing to look for changes (mutations) in the ABCD1 gene, and skin biopsy also may be used.
Genetic counseling is recommended for people with a family history of adrenomyeloneuropathy or other forms of adrenoleukodystrophy. Diagnosis can be made using prenatal testing.
Treatment for adrenoleukodystrophy, due to its complexity and involvement of multiple organ systems, is an effort requiring coordination of multiple specialties, including neurology, endocrinology, physical therapy, and other medical specialists.
People with adrenal insufficiency will need replacement of adrenal steroids, including glucocorticoids (eg, hydrocortisone, prednisone, dexamethasone) and mineralocorticoid (fludrocortisone). In addition, physical therapy and medications may help relieve some of the symptoms of adrenomyeloneuropathy.
Stem cell transplant may be suggested for selected patients with adrenomyeloneuropathy with cerebral involvement. However, the outcome in this group of patients has not been well studied.
People whose disease affects their spine, but not their brain, have better outcomes. In approximately 20% of people, the brain is affected and symptoms get worse over time, possibly resulting in total disability.