Familial hyperlipidemias are classified according to the Fredrickson classification. Type III is also known is familial dysbetalipoproteinemia. It is mainly linked to an increase of IDL. This is caused by APOE. APOE has multiple types, and is part of LDL, IDL, VLDL and chylomicrons. APOE also binds to LDLR, which is required for normal catabolism of triglycerid-rich proteins. Specifically APOE2 is linked with to IDL and because of this, mutations in APOE2 will lead to dysbetalipoproteinemia.