Familial chylomicronemia syndrome (FCS) is a rare disorder of triglyceride (TG) metabolism caused by loss of function variants in one of five known canonical genes involved in chylomicron lipolysis and clearance—LPL, APOC2, APOA5, LMF1, and GPIHBP1. The gene discussed is GPIHBP1; the disease is familial chylomicronemia syndrome.