The plasma samples from the patients with unexplained hypertriglyceridemia and without mutations in LPL or GPIHBP1 at lipid clinics (n = 130), and six patients from unexplained hypertriglyceridemia, including three patients with systemic lupus erythematosus, were positive for GPIHBP1 autoantibodies, and they were complicated by severe hypertriglyceridemia and pancreatitis. The gene discussed is GPIHBP1; the disease is hypertriglyceridemia.