Primary HTG, also known as familial chylomicronemia (FCS), occurs when there are homozygous or compound heterozygous rare variants in six canonical genes involved in the TG metabolism, such as lipoprotein lipase (LPL), apolipoprotein C2 (APOC2), GPI-anchored HDL-binding protein 1 (GPIHBP1), apolipoprotein A5 (APOA5), lipase maturation factor 1 (LMF1) and glucokinase regulator protein (GCKR) (12,13). The gene discussed is LMF1; the disease is familial lipoprotein lipase deficiency.