A young man presents to his physician's office for a physical exam. He is concerned because his father died of a hea attack in his late 40's. The physician finds that he has elevated serum cholesterol and LDL levels, but his VLDL and triglycerides are normal. Fuher investigation reveals an LDL receptor deficiency. This patient has which of the following types of hyperlipidemia?

There are many clues in the question that should have guided you to this choice. The laboratory findings are classic for Type IIa hyperlipidemia. These patients have LDL receptor deficiencies and are at a great risk of advanced coronary atherosclerosis. Since it is autosomal dominant, the patient's father could have been affected as well. Type I hyperlipidemia, or familial hyperchylomicronemia, is caused by a lipoprotein lipase deficiency. These patients have high serum triglycerides and normal cholesterol. They do not have a substantially higher risk of atherosclerosis. Type IIb hyperlipidemia, or familial combined hyperlipidemia, presents as elevated serum LDL, VLDL, cholesterol, and triglycerides. These patients do have an increased incidence of atherosclerosis. Type III hyperlipidemia, or familial dysbetalipoproteinemia, presents as increased serum cholesterol and triglycerides. The mode of inheritance is not understood, but apoprotein E is affected and the risk of atherosclerosis is great. 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.