Cover: Proposed molecular mechanism for mitochondrial impairment in X-linked adrenoleukodystrophy. As C26:0 cannot enter peroxisomes for degradation due to the loss of the peroxisomal transporter ABCD1, it accumulates intracellularly affecting the inner mitochondrial membrane impermeability by unknown mechanisms. This alteration may allow a proton flux into the matrix decreasing Δψm, together with a certain extent of electron leakage promoting ROS formation. These ROS oxidise mitochondrial proteins of TCA cycle and OXPHOS, leading to impaired bioenergetics and respiration, and also oxidise mtDNA, contributing to a devil cycle of mitochondrial dysfunction and ultimately, cell demise. See article by López-Erauskin et al., pp. 3296–3305.