Familial hypobetalipoproteinemia (FHBL), the only CDDENT that is dominantly inherited, is associated with mutations in the APOB gene, encoding apolipoprotein B (Young et al., 1990), which, together with triglycerides and other lipids, makes up the nascent chylomicron (Fig. 4). Here, APOB is linked to familial hypobetalipoproteinemia 1.