The primary cargo glucosylceramide is transported to the maturing LBs by the ABC transporter ABCA12 localized on its limiting membrane, and accordingly, the loss of function mutations of ABCA12 blocks LB biogenesis/maturation, resulting in the fatal condition Harlequin ichthyosis (Akiyama, 2011; Scott et al., 2013). The gene discussed is ABCA12; the disease is Harlequin ichthyosis.