Adrenoleukodystrophy (ALD) is a rare genetic disorder that affects approximately 1 in 20,000 people worldwide. It is caused by a mutation in the ABCD1 gene, which is located on the X chromosome. This gene encodes for a protein that is responsible for transporting very long-chain fatty acids (VLCFAs) out of the cells. When this gene is mutated, VLCFAs accumulate in the brain and other organs, causing damage and leading to the symptoms of ALD.
The major form of ALD is X-linked adrenoleukodystrophy (X-ALD), which is caused by a mutation in the ABCD1 gene. X-ALD is estimated to affect 1 in 17,000 males worldwide. It is also the most common form of ALD.
The other forms of ALD are less common and account for a very small percentage of cases. They include autosomal recessive (AR) ALD, which is caused by a mutation in the ALDP gene, and adrenomyeloneuropathy (AMN), which is caused by a mutation in the ABCD2 gene. These forms of ALD are estimated to affect 1 in 500,000 and 1 in 200,000 people, respectively.
In total, there are approximately 1 in 20,000 cases of adrenoleukodystrophy worldwide. X-ALD is the most common form, but the other forms of ALD are still very rare.