APOA5 and familial chylomicronemia syndrome: First, familial chylomicronemia syndrome (FCS) is an inherited autosomal recessive disease caused by mutations in the lipoprotein lipase (LPL) gene or, more rarely, by loss-of-function mutations in apolipoprotein C-II (APOC2), apolipoprotein A-V (APOA5), glycosyl-phosphatidylinositol anchored high-density lipoprotein-binding protein 1 (GPIHBP1) and lipase maturation factor 1 (LMF1) genes encoding proteins related to its modulation [6].