Familial hyperlipidemias are classified according to the Fredrickson classification. Type IV familial hyperlipidemia is also known as familial hypertriglyceridemia. Typ IV is mostly linked to in increased VLDL within the blood. This is from both an increased production as well as a decreased elimination of VLDL.
The increased production is caused by mutations of GCKR. This gene inhibits glucokinase, which would lead to less triglycerides produced in the liver. These triglycerides would then increase the amount of VLDL in the blood. Mutations in GCKR would therefore lead to increased VLDL.
A decreased elimination is caused by APOA5. APOA5 plays a role in the hydrolysis of VDLD by LPL. Mutations in this gene would therefore lead to a decrease of this hydrolysis.