On laboratory investigations in a patient, LDL was highly elevated but the level of LDL receptors was normal. Which of the following is most probable cause?
(A) Phosphorylation of LDL receptors (B) Lipoprotein lipase deficiency (C) Apo B-100 mutation (D) Cholesterol Acyl Co-A transferase deficiency
(C) Ans: C. Apo B-100 mutationIn Type Ila Familial hypercholesterolemia:Highly elevated levels of LDL with normal level of LDL receptors.Characterized mutation in ligand region of apoB-100.Differential diagnosis:"Familial Defective apoB-100 (FDB)"/"Autosomal dominant hypercholesterolemia (ADH) type 2":Dominantly inherited disorder.Clinically resembles heterozygous familial hypercholesterolemia (FH) with elevated LDL-C levels and normal TGs.FDB - Caused by mutations in gene encoding apoB-100, specifically in LDL receptor-binding domain of apoB-100.Ref (Harrison 19/e p2438-2447, 18/e p3148)