This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lipoproteins, Subject name: Biochemistry
[{'content': 'A patient was found to have high LDL, increased total cholesterol. But normal levels of LDL-Receptors. What is the most probable cause: \nSelect and explain. \nA. Apo B100 mutation, B. Apo E defect, C. LCAT Deficiency, D. Lipoprotein lipase Deficiency', 'role': 'user'}, {'content': 'Answer: A \nExplanation: This is Familial defective Apo B100, also known as Autosomal Dominant Hypercholesterolemia IIa. There is a mutation in the gene encoding Apo B100, specifically in LDL-receptor binding domain of Apo B100.', 'role': 'assistant'}]