What does it mean to be a carrier for X-linked adrenoleukodystrophy?
Only women can be carriers of adrenoleukodystrophy. Carriers of X-linked adrenoleukodystrophy have a change in one of their ABCD1 genes but also have another copy that is functioning properly. Females can be carriers because they have two copies of the X chromosome and therefore two copies of ABCD1. Most women who are carriers do not show signs and symptoms of the condition, but an estimated 20% of carrier females will show moderate paraparesis (difficulty using the lower limbs), usually in middle age or later life.
Males cannot be carriers because they only have one X chromosome. Therefore, if a male has a change to ABCD1, he has no normally functioning copy of that gene, and will express adrenoleukodystrophy in some way.
Steinberg, S., Moser, A., Raymond, G. X-Linked Adrenoleukodystrophy. Gene Reviews. Online database. Updated April 2015. http://www.ncbi.nlm.nih.gov/books/NBK1315/
X-Linked Adrenoleukodystrophy. Genetics Home Reference. Updated July 2013.https://ghr.nlm.nih.gov/condition/x-linked-adrenoleukodystrophy