VLCFAs are produced within all cells by the elongation of long-chain fatty acids (LCFA) and through dietary intake. Following transport of VLCFA via the membrane ATP-binding cassette (ABC) transporter into the peroxisome, the degradation into acyl coenzyme A (acyl CoA) derivatives occurs. Mutations in the ABCD1 gene cause dysfunction of the ABC transporter, resulting in accumulation of VLCFA (>C22 length, particularly C24:0, C24:1 and C26:0) leading to dysfunction within the adrenal gland and nervous system (box). LCFA, long-chain-fatty acid; VLCFA, very-long-chain fatty acid; Acyl-CoA, acyl coenzyme A; ABCD1, ATP-binding cassette domain 1; Cx, fatty acid with x carbon chain length.