ABCB4 and X-linked adrenoleukodystrophy: Some ABC genes have been associated with hereditary diseases such as cystic fibrosis caused by mutations in ABCC7/CFTR (cystic fibrosis transmembrane conductance regulator), adrenoleukodystrophy (ALD) caused by mutations in ABCD1, and cholesterol metabolism disorders caused by mutations in ABCB4, ABCB11, and ABCC2 [13].