Acquired lipoprotein lipase deficiency associated with chronic urticaria. A new etiology for type I hyperlipoproteinemia

Approach to Hypertriglyceridemia in the Pediatric Population

Hypertriglyceridemia is increasingly identified in children and adolescents, owing to improved screening and higher prevalence of childhood obesity. Hypertriglyceridemia can result from either increased triglyceride (TG) production or reduced TG clearance. The etiologic origin can be primary (genetic) or secondary, but it is often multifactorial. Management is challenging because of the interplay of genetic and secondary causes and lack of evidence-based guidelines. Lifestyle changes and dietary interventions are most important, especially in hypertriglyceridemia associated with obesity. Dietary restriction of fat remains the mainstay of management in primary hypertriglyceridemia. When fasting TG concentration is increased above 500 mg/dL (5.65 mmol/L), fibrates may be used to prevent pancreatitis. Omega-3 fatty acids are often used as an adjunctive therapy. When the fasting TG concentration is less than 500 mg/dL (5.65 mmol/L) and if the non-high-density lipoprotein cholesterol level is above 145 mg/dL (3.76 mmol/L), statin treatment can be considered.

Paediatric type III dyslipidaemia: a case of vanishing hyperlipidaemia

An 11-year-old girl presented with palmar and tuberoeruptive xanthomas, and elevated triglycerides and total cholesterol levels. She had an apolipoprotein E2/E2 genotype. A diagnosis of type III dyslipidaemia was made and the patient started on niacin, fenofibrate and salmon oil. At age 18, her lipid levels were well controlled with fenofibrate once weekly. At age 21, the fenofibrate was discontinued and her lipid profile has been normal for the last 4 years. This case history may be consistent with a transient dyslipidaemia.

Type 1 hyperlipoproteinemia and recurrent acute pancreatitis due to lipoprotein lipase antibody in a young girl with Sjogren's syndrome

CONTEXT

Type 1 hyperlipoproteinemia (T1HLP) in childhood is most often due to genetic deficiency of lipoprotein lipase (LPL) or other related proteins.

OBJECTIVE

The aim was to report a case of marked hypertriglyceridemia and recurrent acute pancreatitis due to the presence of LPL autoantibody in a young girl who was subsequently diagnosed with Sjögren's syndrome.

SUBJECT AND METHODS

A 9-yr-old African-American girl presented with acute pancreatitis and serum triglycerides of 4784 mg/dl. Strict restriction of dietary fat reduced serum triglycerides, but she continued to experience recurrent pancreatitis. Approximately 18 months thereafter, she developed transient pauciarticular arthritis with elevated serum antinuclear antibody (>1:1280). Minor salivary gland biopsy revealed chronic sialadenitis with a dense periductal lymphocytic aggregate suggestive of Sjögren's syndrome. Genomic DNA was analyzed for LPL, GPIHBP1, APOA5, APOC2, and LMF1. Immunoblotting was performed to detect serum LPL autoantibody.

RESULTS

The patient had no disease-causing variants in LPL, GPIHBP1, APOA5, APOC2, or LMF1. Immunoblotting revealed serum LPL antibody. The patient responded to immunosuppressive therapy for Sjögren's syndrome with resolution of hypertriglyceridemia.

CONCLUSIONS

Unexplained T1HLP in childhood could be secondary to LPL deficiency induced by autoantibodies. Therefore, diagnosis of autoimmune T1HLP should be entertained if clinical features are suggestive of an autoimmune process.

A case of adolescent hyperlipoproteinemia with xanthoma and acute pancreatitis, associated with decreased activities of lipoprotein lipase and hepatic triglyceride lipase

Lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) enhance the hydrolysis of triglycerides (TG) transported by chylomicron (CM) and very-low-density lipoprotein (VLDL). We report a case of severe hyperchylomicronemia with high levels of remnant lipoprotein and total cholesterol (T-Chol) in a 15-year-old boy. Precise examination of the lipid profile showed decreased activities of both LPL and HTGL, although the protein mass for LPL and HTGL were maintained. In addition, bezafibrate treatment effectively ameliorated hypertriglyceridemia in this case. This is the first case of hyperchylomicronemia with decreased activities and unaffected protein masses for both LPL and HTGL, without overt immuno-dysfunction.

Two cases with transient lipoprotein lipase (LPL) activity impairment: evidence for the possible involvement of an LPL inhibitor

Two independent severe hypertriglyceridemic infants with transiently impaired lipoprotein lipase (LPL) activity were observed and the causes were explored. Both infants were female, born prematurely with low birth weight and developed hypertriglyceridemia (Fredrickson type V hyperlipidemia: high VLDL and low LDL/HDL) a few months after birth. While mass levels of their post-heparin plasma LPL and apoprotein C-II (apo C-II), a physiological activator of LPL, were normal, their post-heparin plasma LPL activities were remarkably impaired. Both of their mothers' post-heparin plasma LPL activities were slightly or moderately impaired as well, without a decrease in the LPL mass level. No mutations in the genes for LPL and apo C-II were detected in either patient. In an in vitro study with their serum at onset, we could not detect any distinct circulating inhibitors for LPL. There was no data supporting infection or autoimmune diseases, which might have an impact on LPL activity, during the follow-up period. Levels of their plasma triglyceride (TG) and total cholesterol (TC) were decreased quickly by a dietary intervention with medium-chain triglyceride (MCT) milk and kept normal even after stopping the intervention at around age 1 year. However, their low post-heparin LPL activity persisted and returned to normal at around age 2 years. Their low HDL cholesterol levels persisted even after recovery of the TG and TC levels, although lecithin:cholesterol acyltransferase (LCAT) and cholesterol-ester-transfer protein (CETP), two key enzymes of HDL metabolism, were normal throughout the course. The exact reasons why their post-heparin LPL activities were impaired for a certain period and why their HDL cholesterol levels have remained low are still unclear.

CONCLUSION

Transiently impaired LPL activity with no defect in LPL enzyme induced severe hypertriglyceridemia in infants. The transient occurrence of inhibitor(s) for LPL was proposed.