Adrenoleukodystrophy (ALD) is an inherited metabolic storage disorder. An inherited disorder means that the disease is caused by a faulty gene passed on from parent(s) to children. Genes are instructions that tell the body how to make all the different substances the body needs to work properly. The affected gene in ALD prevents the body from being able to break down (metabolize) certain fatty acids.
The faulty gene that causes ALD is on the X chromosome. Chromosomes are thread-like strands of DNA that carry genetic information about your body. Boys have one X and one Y chromosome. Since boys have only one X chromosome, if it carries a faulty gene, they will typically have severe disease. About 1 out of every 3 boys born with ALD will have the most severe form called cerebral ALD. In contrast, girls inherit an X chromosome from each parent. Since girls with ALD usually have one faulty and one normal gene, they often have milder disease and may not be diagnosed until adulthood.
The faulty gene involved in ALD prevents the body from being able to break down certain fatty acids. Fatty acids make up the fat in our bodies. These fatty acids build up in the brain and spinal cord and keep nerve cells from sending signals throughout the body. As a result, those severely affected with ALD will have problems with memory, learning, speaking, other mental functions, and movement. Fatty acids may also build up in the adrenal glands (small glands that sit on the kidneys) and result in the glands not making enough hormones.