APOA5 and familial chylomicronemia syndrome: Familial chylomicronemia syndrome (FCS, OMIM #238600) is a rare autosomal recessive disorder resulting from the deficiency of lipoprotein lipase (LPL, 8p21.3), apoprotein C2 (APOC2, 19q13.32), apolipoprotein A5 (APOA5, 11q23.3), lipase maturation factor 1 (LMF1, 16p13.3), glycosylphosphatidylinositol‐anchored‐high‐density lipoprotein‐binding protein 1 (GPIHBP1, 8q24.3), and glycerol‐3‐phosphate dehydrogenase 1 (GPD1, 12q13.12), with additional genes expected to be identified in the future.1