A 6-year-old boy is brought to the emergency department after a traumatic fall from his bicycle. Physical examination shows a large laceration over his left leg that is irrigated and closed with sutures. While he is receiving care, a routine blood draw shows milky plasma that forms a creamy-appearing supernatant upon standing. Further testing shows that his plasma lipoprotein lipase activity measured after intravenous heparin administration is substantially lower than normal. If his condition remains untreated, this patient is most likely to develop which of the following features?

Question

A 6-year-old boy is brought to the emergency department after a traumatic fall from his bicycle.  Physical examination shows a large laceration over his left leg that is irrigated and closed with sutures.  While he is receiving care, a routine blood draw shows milky plasma that forms a creamy-appearing supernatant upon standing.  Further testing shows that his plasma lipoprotein lipase activity measured after intravenous heparin administration is substantially lower than normal.  If his condition remains untreated, this patient is most likely to develop which of the following features?

Quizplus · Accepted Answer

11ec160b_3914_0fce_9249_9953ce19d530_MD0001_00 This patient has familial chylomicronemia syndrome (type 1 hyperlipoproteinemia), an autosomal recessive condition most often caused by lipoprotein lipase (LPL) deficiency. LPL is normally bound to heparan sulfate moieties on the vascular endothelium, allowing it to interact with chylomicrons and VLDL in the circulation and release free fatty acids into the adjacent tissues. Heparin administration releases these endothelium-bound lipases, allowing LPL activity to be measured in the laboratory. Without sufficient LPL activity, the body is unable to clear dietary lipid loads due to defective hydrolysis of serum triglycerides (especially chylomicrons). Patients with familial chylomicronemia syndrome present in childhood with marked hypertriglyceridemia, recurrent acute pancreatitis, lipemia retinalis (milky-appearing retinal vasculature), and eruptive xanthomas (small yellowish papules surrounded by erythema found mainly on extensor surfaces). (Choice B) The familial hyperlipoproteinemias are not associated with intellectual disability. (Choices C, D, and E) Accelerated coronary artery disease, tendon xanthomas (nodular lipid deposits in the tendons, particularly the Achilles), and xanthelasmas are seen in familial hypercholesterolemia, a condition caused by defects in the LDL receptor or its ligand, ApoB-100. As LDL is mainly cleared from the circulation by receptor-mediated uptake in the liver, individuals with familial hypercholesterolemia have dramatically elevated LDL concentrations. Educational objective: Familial chylomicronemia syndrome frequently presents in childhood with recurrent episodes of acute pancreatitis. Patients with this disorder are not usually at increased risk for premature coronary artery disease. Eruptive skin xanthomas may be present in hypertriglyceridemia, but tendon xanthomas and xanthelasmas are primarily seen with hypercholesterolemia.

A 6-Year-Old Boy Is Brought to the Emergency Department After