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Familial chylomicronemia syndrome (FCS) is a rare genetic disorder characterized by extremely high triglyceride levels due to impaired clearance of chylomicrons from plasma. This paper is the result of a panel discussion with Latin American specialists who raised the main issues on diagnosis and management of FCS in their countries. Overall FCS is diagnosed late on the course of the disease, is characterized by heterogeneity on the occurrence of pancreatitis, and remains a long time in care of different specialists until reaching a lipidologist. Pancreatitis and secondary diabetes are frequently seen, often due to late diagnosis and inadequate care. Molecular diagnosis is unusual; however, loss of function variants on the lipoprotein lipase gene are apparently the most frequent etiology. A founder effect of the glycosylphosphatidylinositol anchored high density lipoprotein binding protein 1 gene has been described in the northeast of Brazil. Low awareness of the disease amongst health professionals contributes to inadequate care and an inadequate patient journey., (Copyright © 2021 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: Chylomicronemia syndrome (CS) is a metabolic condition characterized by severely elevated plasma triglycerides (>880 mg/dL) and high rates of morbidity and mortality. The syndrome can be classified into two major groups: monogenic familial chylomicronemia syndrome (FCS) and multifactorial chylomicronemia syndrome (MCS), the frequencies of which are ill-defined., Objective: The objective of the study was to characterize the prevalence of the most common and rarest subsets of this syndrome, MCS and FCS, respectively, in a single-center, real-world setting., Methods: This was a retrospective cross-sectional study of patients with plasma triglycerides ≥880 mg/dL. The criteria used for identification of patients with FCS were modeled after a Food and Drug Administration endorsed set of parameters. Less stringent criteria that removed the requirement for pancreatitis were used to classify MCS. Full criteria are described in detail in the article., Results: Of the 2,342,136 patient records queried, 578 had triglycerides ≥880 mg/dL (0.025%), of which 86 had a documented history of pancreatitis. Five patients who met the criteria for FCS were identified (three genetically confirmed), resulting in an estimated prevalence of ~1-2 per 1,000,000. On the other hand, MCS was identified in 186 patients, corresponding to an estimated prevalence of ~1 in 12,000. There were 5181 cases of pancreatitis (0.22% of the entire cohort), 86 of which occurred in subjects with triglycerides≥880 mg/dL (1.7% of cases of pancreatitis). Rates of pancreatitis in this subset were elevated at 6.5%, 100%, and 17.8%, among patients with MCS, FCS, and secondary hypertriglyceridemia, respectively., Conclusions: CS is an uncommon condition, but it is associated with significant complications, regardless of etiology. Among patients with CS, MCS was 40- to 60-fold more prevalent than FCS and associated with frequent morbidity. Therefore, disease recognition and treatment should extend to all forms of CS pursuant to the clinical presentation., (Copyright © 2020 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Familial chylomicronemia syndrome is characterized by severe elevation in serum triglycerides and an increased risk of acute pancreatitis. Although familial chylomicronemia syndrome is mainly caused by mutations in the lipoprotein lipase (LPL) gene, few causal mutations in other genes (ie, APOC2, APOA5, LMF1, and GPIHBP1) have also been reported. In this case report, we present the discovery of a novel mutation in the glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) gene and discuss its pathogenicity through a familial segregation study., (Copyright © 2018 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Plasma triglyceride concentrations are normally below 150 mg/dL in the fasting state. However, these lipids can reach values of several thousand mg/dL. Elevations in this range are due to a massive retention of chylomicrons and usually result from multiple genetic variants with superimposed influences such as diabetes and immune disorders. Less commonly, major gene defects in lipoprotein metabolism can be the cause. These may present soon after birth with strong evidence of familial penetrance. The causes of this syndrome have been discussed in a Roundtable published in the most recent issue of this Journal. The polygenic etiology may also have a familial presentation with similar clinical import. The diagnosis and management of these disorders is of importance since they can lead to critical clinical syndromes including death from acute hemorrhagic pancreatitis. The chronic management requires a dedicated medical team and a patient committed to an effective regimen. We are joined in this discussion by Dr P. Barton Duell, University of Oregon Health Sciences Center, and Dr Daniel Gaudet of the Université de Montreal, Montreal, Quebec. All have had extensive personal experience in the diagnosis and management of patients with familial chylomicronemia. This Roundtable was recorded on November 11, 2017, during a meeting of the National Lipid Association in New Orleans, Louisiana., (Copyright © 2018 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: The incidental finding of severe hypertriglyceridemia (HyperTG) in a child may suggest the diagnosis of familial chylomicronemia syndrome (FCS), a recessive disorder of the intravascular hydrolysis of triglyceride (TG)-rich lipoproteins. FCS may be due to pathogenic variants in lipoprotein lipase (LPL), as well as in other proteins, such as apolipoprotein C-II and apolipoprotein A-V (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface) and LMF1 (a factor required for intracellular formation of active LPL)., Objective: Molecular characterization of 5 subjects in whom HyperTG was an incidental finding during infancy/childhood., Methods: We performed the parallel sequencing of 20 plasma TG-related genes., Results: Three children with severe HyperTG were found to be compound heterozygous for rare pathogenic LPL variants (2 nonsense, 3 missense, and 1 splicing variant). Another child was found to be homozygous for a nonsense variant of APOA5, which was also found in homozygous state in his father with longstanding HyperTG. The fifth patient with a less severe HyperTG was found to be heterozygous for a frameshift variant in LIPC resulting in a truncated Hepatic Lipase. In addition, 1 of the patients with LPL deficiency and the patient with APOA-V deficiency were also heterozygous carriers of a pathogenic variant in LIPC and LPL gene, respectively, whereas the patient with LIPC variant was also a carrier of a rare APOB missense variant., Conclusions: Targeted parallel sequencing of TG-related genes is recommended to define the molecular defect in children presenting with an incidental finding of HyperTG., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

We report a case of severe type I hyperlipoproteinemia caused by autoimmunity against lipoprotein lipase (LPL) in the context of presymptomatic Sjögren's syndrome. A 7-year-old mixed race (Caucasian/African American) girl was admitted to the intensive care unit at Vanderbilt Children's Hospital with acute pancreatitis and shock. She was previously healthy aside from asthma and history of Hashimoto's thyroiditis. Admission triglycerides (TGs) were 2191 mg/dL but returned to normal during the hospital stay and in the absence of food intake. At discharge, she was placed on a low-fat, low-sugar diet. She did not respond to fibrates, prescription fish oil, metformin, or orlistat, and during the following 2 years, she was hospitalized several times with recurrent pancreatitis. Except for a heterozygous mutation in the promoter region of LPL, predicted to have no clinical significance, she had no further mutations in genes known to affect TG metabolism and to cause inherited type I hyperlipoproteinemia, such as APOA5, APOC2, GPIHBP1, or LMF1. When her TG levels normalized after incidental use of prednisone, an autoimmune mechanism was suspected. Immunoblot analyses showed the presence of autoantibodies to LPL in the patient's plasma. Autoantibodies to LPL decreased by 37% while patient was on prednisone, and by 68% as she subsequently transitioned to hydroxychloroquine monotherapy. While on hydroxychloroquine, she underwent a supervised high-fat meal challenge and showed normal ability to metabolize TG. For the past 3 years and 6 months, she has had TG consistently <250 mg/dL, and no symptoms of, or readmissions for, pancreatitis., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: GPIHBP1, a glycolipid-anchored protein of capillary endothelial cells, binds lipoprotein lipase (LPL) in the interstitial spaces and transports it to the capillary lumen. GPIHBP1 deficiency prevents LPL from reaching the capillary lumen, resulting in low intravascular LPL levels, impaired intravascular triglyceride processing, and severe hypertriglyceridemia (chylomicronemia). A recent study showed that some cases of hypertriglyceridemia are caused by autoantibodies against GPIHBP1 ("GPIHBP1 autoantibody syndrome")., Objective: Our objective was to gain additional insights into the frequency of the GPIHBP1 autoantibody syndrome in patients with unexplained chylomicronemia., Methods: We used enzyme-linked immunosorbent assays to screen for GPIHBP1 autoantibodies in 33 patients with unexplained chylomicronemia and then used Western blots and immunocytochemistry studies to characterize the GPIHBP1 autoantibodies., Results: The plasma of 1 patient, a 36-year-old man with severe hypertriglyceridemia, contained GPIHBP1 autoantibodies. The autoantibodies, which were easily detectable by Western blot, blocked the ability of GPIHBP1 to bind LPL. The plasma levels of LPL mass and activity were low. The patient had no history of autoimmune disease, but his plasma was positive for antinuclear antibodies., Conclusions: One of 33 patients with unexplained chylomicronemia had the GPIHBP1 autoantibody syndrome. Additional studies in large lipid clinics will be helpful for better defining the frequency of this syndrome and for exploring the best strategies for treatment., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: Type 1 hyperlipoproteinemia is a rare autosomal recessive disorder most often caused by mutations in the lipoprotein lipase (LPL) gene resulting in severe hypertriglyceridemia and pancreatitis., Objectives: The aim of this study was to identify novel mutations in the LPL gene causing type 1 hyperlipoproteinemia and to understand the molecular mechanisms underlying the severe hypertriglyceridemia., Methods: Three patients presenting classical features of type 1 hyperlipoproteinemia were recruited for DNA sequencing of the LPL gene. Pre-heparin and post-heparin plasma of patients were used for protein detection analysis and functional test. Furthermore, in vitro experiments were performed in HEK293 cells. Protein synthesis and secretion were analyzed in lysate and medium fraction, respectively, whereas medium fraction was used for functional assay., Results: We identified two novel mutations in the LPL gene causing type 1 hyperlipoproteinemia: a two base pair deletion (c.765&#95;766delAG) resulting in a frameshift at position 256 of the protein (p.G256TfsX26) and a nucleotide substitution (c.1211 T > G) resulting in a methionine to arginine substitution (p.M404 R). LPL protein and activity were not detected in pre-heparin or post-heparin plasma of the patient with p.G256TfsX26 mutation or in the medium of HEK293 cells over-expressing recombinant p.G256TfsX26 LPL. A relatively small amount of LPL p.M404 R was detected in both pre-heparin and post-heparin plasma and in the medium of the cells, whereas no LPL activity was detected., Conclusions: We conclude that these two novel mutations cause type 1 hyperlipoproteinemia by inducing a loss or reduction in LPL secretion accompanied by a loss of LPL enzymatic activity., (Copyright © 2016 National Lipid Association. Published by Elsevier Inc. All rights reserved.)