A patient was diagnosed with isolated increase in LDL. His father and brother had the same disease with increased cholesterol. The likely diagnosis is

Type II A (Primary familial hypercholesterolemia) There is elevation of LDL. Patients seldom survive the second decade of life due to ischemic hea disease .The cause is LDL receptor defect. Receptor deficiency in liver and peripheral tissues will result in the elevation of LDL levels in plasma, leading to hypercholesterolemia. The LDL receptor defect may be due to the following reasons: 1. LDL receptor deficiency. 2. Defective binding of B-100 to the receptor. A substitution of glutamine for arginine at 3500thamino acid results in poor binding to LDL receptors. This defect is known as B-3500 or familial defective apo-B. 3. Receptor-LDL complex is not internalised. Secondary type II hyperlipoproteinemia is seen in hypothyroidism, diabetes mellitus, nephrotic syndrome and cholestasisRef: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 300