ABCD1 and X-linked adrenoleukodystrophy: ABCD1 gene defect leads to the accumulation of straight, saturated, very-long-chain fatty acids (those containing more than 22 carbons) in nervous and peripheral tissues and organs, eventually leading to one of the main phenotypes adrenomyeloneuropathy (AMN) or cerebral ALD (CALD), the severe inflammatory and demyelinating form of X-ALD.