A 20-year-old man comes to the physician because of recurrent episodes of acute abdominal pain since childhood. The pain usually occurs after eating a meal with a rich dessert. Physical examination shows a small number of xanthomas on the buttocks and knees. A fasting lipid analysis shows milky plasma; there is markedly increased serum concentration of triglycerides and chylomicrons. His serum LDL-cholesterol concentration is within the reference range, and serum HDL-cholesterol concentration is decreased. This patient most likely has a defect of which of the following proteins?

Question

Quizplus · Accepted Answer

The patient's symptoms and laboratory findings are consistent with familial chylomicronemia syndrome, which is often due to a deficiency of lipoprotein lipase or its cofactor, apoC-II. This leads to the accumulation of chylomicrons and very high triglyceride levels.  ApoC-II is present in chylomicrons, LDL, and HDL and is required for the activation of the endothelial cell-associated triglyceride lipase called lipoprotein lipase (LPL). Loss, or defective activity, of apoC-II would result in circulating lipoproteins of all types enriched in triglyceride leading to hypertriglyceridemia. Additional symptoms associated with apoCII deficiency include eruptive xanthomas, pancreatitis, and hepatosplenomegaly. The hepatosplenomegaly is the cause of the acute abdominal pain

A 20-Year-Old Man Comes to the Physician Because of Recurrent