Although the precise function of ALDP is still unknown, the excessive accumulation of VLCFA in X-ALD patients [63] and mice [45], [46], [47], and deficient β-oxidation of these FAs in cells derived from X-ALD patients [4], [64] indicate that it is related to the metabolism of VLCFA in peroxisomes [4], [65]. Here, ABCD1 is linked to X-linked adrenoleukodystrophy.