In addition to saturated VLCFA, there is also accumulation of monounsaturated fatty acids (C26∶1) in plasma, fibroblasts and brain of X-ALD patients as well as in Abcd1-KO mouse indicating that β-oxidation of C26∶1 is also reduced in X-ALD [48], [49]. Here, ABCD1 is linked to X-linked adrenoleukodystrophy.