APOE and hyperlipoproteinemia type 3: Subsequently, it was discovered that LPG is caused by mutations in the apolipoprotein E (ApoE) gene.[3] To date, approximately 14 different ApoE gene variants have been identified in association with LPG.[4,5] Patients with LPG often exhibit abnormalities in lipid metabolism (similar to type III hyperlipoproteinemia) and elevated concentrations of ApoE, as well as varying degrees of proteinuria.