APOA5 and familial chylomicronemia syndrome: Familial chylomicronemia syndrome is a rare monogenic disorder due to mutations in the LPL gene leading to reduced levels of enzyme lipoprotein lipase, or mutation of genes encoding regulators of lipoprotein lipase, GPIHBP1, APOA5, APOC2, and LMF1. Multifactorial chylomicronemia syndrome is more common than familial chylomicronemia syndrome, affecting 1 in 600 of the population (21).