X-linked adrenoleukodystrophy (X-ALD) is a monogenic disease caused by mutations in the ABCD1 gene located on Xq28. It is passed down from parents to their children as an X-linked genetic trait. It therefore affects mostly males, although some women who are carriers can have milder forms of the disease. The condition results in the buildup of very-long-chain fatty acids in the nervous system, adrenal gland, and testes, which disrupts normal activity.

Adrenoleukodystrophy is passed down from parents to their children as an X-linked genetic trait. It therefore affects mostly males, although some women who are carriers can have milder forms of the disease. It affects approximately 1 in 20,000 people from all races.

The condition results in the buildup of very-long-chain fatty acids in the nervous system, adrenal gland, and testes, which disrupts normal activity. There are different types of ALD, with a range of symptoms and differing ages of onset, but the underlying cause of the disease is the same in each type: a mutation, or a change, in the ABCD1 gene. ^[1] There are three major categories of disease:

• Childhood cerebral form — appears in mid-childhood (at ages 4 – 8)
• Adrenomyelopathy — occurs in men in their 20s or later in life
• Impaired adrenal gland function (called Addison disease or Addison-like phenotype) — adrenal gland does not produce enough steroid hormones