PEX26 and peroxisome biogenesis disorder: To test if the induction of peroxisomal β-oxidation by BF caused the reduction in C26:0 levels, we incubated fibroblasts from patients with a peroxisomal biogenesis disorder (PEX1, PEX6 and PEX26) with BF and measured the effect on D3-C26:0 de novo synthesis.