A person is diagnosed to have familial type IIa hyperlipoproteinemia. What is the basic defect in this type of hyperlipoproteinemia?

Familial type IIa hypercholesterolemia is associated with a defect in the LDL receptor or with a mutation in ligand region of apo B-100. These patients have elevated levels of cholesterol and LDL which in turn result in atherosclerosis and coronary hea disease. Type I hyperlipoproteinemias is associated with lipoprotein lipase deficiency or apo C II deficiency causing inactive LPL. Type III hyperlipoproteinemias is due to abnormality in apo E. Type IV hyperlipoproteinemias is due to overproduction of VLDL. Ref: Botham K.M., Mayes P.A. (2011). Chapter 26. Cholesterol Synthesis, Transpo, & Excretion. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.