X-linked adrenoleukodystrophy; Melanodermic leukodystrophy; Adrenoleukodystrophy; NALD
Adrenoleukodystrophy describes any of several closely related inheritable disorders of the breakdown (metabolism) of certain fats (long chain fatty acids). These disorders affect the adrenal glands, nervous system, and testes.
Causes, incidence, and risk factors
Adrenoleukodystrophy is transmitted as an X-linked trait (the neonatal form is by autosomal recessive transmission). It affects approximately 1 in 20,000 to 1 in 50,000 individuals from all races.
It results in the accumulation of long chain fatty acids in the nervous system, adrenal gland, and testes, which disrupts normal activity. There are several (seven recognized) different forms of the disease.
The neonatal form appears shortly after birth and includes seizures and delayed neurological development with death occurring in infancy or young childhood. The childhood cerebral form appears in mid-childhood (at 4-8 years), and the other forms appear during adolescence. About one-third of affected people develop neurological symptoms and about half develop abnormal adrenal function.
In the childhood form, early symptoms include hyperactivity, difficulty at school, difficulty understanding spoken material, deterioration of handwriting, crossed eyes (strabismus), and possibly seizures.
As the disease progresses, further signs of damage to the white matter of the brain appear and include changes in muscle tone, stiffness and contracture deformities, swallowing difficulties, and coma.
The other major component of adrenoleukodystrophy is the development of impaired adrenal gland function (similar to Addison disease). There is a deficiency of steroid hormones. This is a very significant development but one that can be adequately treated with corticosteroids.
- delayed neurological development
- frequent respiratory infections
- darkening of the skin color (increased skin pigmentation)
Childhood and adolescent type:
- decreasing school performance
- decreased understanding of verbal communication (aphasia)
- crossed eyes
- swallowing difficulties
- changes in muscle tone, especially muscle spasms and spasticity
Progressive nervous system deterioration
- hearing loss
- visual impairment or blindness
- deteriorating fine motor control
- eventually may lead to a vegetative state
Symptoms of adrenal gland failure
- muscular weakness (asthenia)
- wasting (loss of weight, muscle mass)
- decreased appetite
- increased skin pigmentation
Signs and tests
- blood levels showing elevated long chain fatty acids
- skin biopsy and fibroblast culture showing elevated levels of long chain fatty acids
- MRI of the head showing damage to the white matter of the brain (white matter is a specific type of brain tissue)
- head CT shows damage to the white matter of the brain
- chromosome study (neolatal form - defects at chromosome 7q21-q22)
Adrenal dysfunction is treated with supplemental steroids (such as cortisol).
A specific treatment for adrenoleukodystrophy is not available, but a diet low in long chain fatty acids and the administration of special oils has been demonstrated to lower the blood levels of the long chain fatty acids. These oils are referred to as Lorenzo’s oil, after the son of the family who discovered the treatment. This regimen is presently under evaluation for the treatment of adrenoleukodystrophy.
The childhood form of adrenoleukodystrophy is a progressive disease that leads to a vegetative state in approximately two years after neurologic symptoms develop. The child may live in this condition for as much as ten years until death occurs. The later onset forms are significantly less dangerous.
- adrenal crisis
- vegetative state (long-term coma)
Calling your health care provider
Call your health care provider if your child develops symptoms suggestive of adrenoleukodystrophy or if you have a child with adrenoleukodystrophy who is experiencing increased difficulty.
Genetic counseling is recommended for prospective parents with a family history of adrenoleukodystrophy. The carrier state in females can be diagnosed in 85% of the cases using a very long fatty acid assay and a DNA probe study by specialized laboratories.
Intrauterine diagnosis of adrenoleukodystrophy is available and done by evaluation of cells from chorionic villus sampling or from amniotic cells (amniocentesis).
by Sharon M. Smith, M.D.