Roundtable discussion: Familial chylomicronemia syndrome: Diagnosis and management

Challenges in familial chylomicronemia syndrome diagnosis and management across Latin American countries: An expert panel discussion

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.

Rare Variants in Triglycerides-Related Genes Increase Pancreatitis Risk in Multifactorial Chylomicronemia Syndrome

CONTEXT

Severe hypertriglyceridemia (fasting triglycerides [TG] concentration ≥10 mmol/L) can be caused by multifactorial chylomicronemia syndrome (MCS) or familial chylomicronemia syndrome (FCS). Both conditions are associated with an increased risk of acute pancreatitis. The clinical differences between MCS patients with or without a rare variant in TG-related genes have never been studied.

OBJECTIVE

To compare the clinical and biochemical characteristics of FCS, positive-MCS patients, and negative-MCS patients, as well as to investigate the predictors of acute pancreatitis in MCS patients.

METHODS

All patients referred at the clinic for severe hypertriglyceridemia underwent genetic testing for the 5 canonical genes involved in TG metabolism (LPL, APOC2, GPIHBP1, APOA5, and LMF1) using next-generation sequencing.

RESULTS

A total of 53 variant negative-MCS, 22 variant positive-MCS and 28 FCS subjects were included in this retrospective cross-sectional study. A significant difference was observed in the prevalence of pancreatitis (9%, 41%, and 61%) and multiple pancreatitis (6%, 23%, and 46%) in the negative-MCS, the positive-MCS, and the FCS groups, respectively (P < 0.0001). Predictors of pancreatitis among MCS subjects included the presence of a rare variant, lower apolipoprotein B, as well as higher gamma-glutamyl transferase, maximal TG value, and fructose consumption.

CONCLUSION

We observed that the MCS individuals who carried a rare variant have an intermediate phenotype between FCS and negative-MCS subjects. Since novel molecules such as the antisense oligonucleotide against APOC3 mRNA showed high efficacy in reducing TG levels in patients with multifactorial chylomicronemia, identification of higher-risk MCS patients who would benefit from additional treatment is essential.

Current Diagnosis and Management of Primary Chylomicronemia

Primary chylomicronemia (PCM) is a rare and intractable disease characterized by marked accumulation of chylomicrons in plasma. The levels of plasma triglycerides (TGs) typically range from 1,000 - 15,000 mg/dL or higher.

PCM is caused by defects in the lipoprotein lipase (LPL) pathway due to genetic mutations, autoantibodies, or unidentified causes. The monogenic type is typically inherited as an autosomal recessive trait with loss-of-function mutations in LPL pathway genes ( LPL , LMF1 , GPIHBP1 , APOC2 , and APOA5 ). Secondary/environmental factors (diabetes, alcohol intake, pregnancy, etc.) often exacerbate hypertriglyceridemia (HTG).

The signs, symptoms, and complications of chylomicronemia include eruptive xanthomas, lipemia retinalis, hepatosplenomegaly, and acute pancreatitis with onset as early as in infancy. Acute pancreatitis can be fatal and recurrent episodes of abdominal pain may lead to dietary fat intolerance and failure to thrive.

The main goal of treatment is to prevent acute pancreatitis by reducing plasma TG levels to at least less than 500-1,000 mg/dL. However, current TG-lowering medications are generally ineffective for PCM. The only other treatment options are modulation of secondary/environmental factors. Most patients need strict dietary fat restriction, which is often difficult to maintain and likely affects their quality of life.

Timely diagnosis is critical for the best prognosis with currently available management, but PCM is often misdiagnosed and undertreated. The aim of this review is firstly to summarize the pathogenesis, signs, symptoms, diagnosis, and management of PCM, and secondly to propose simple diagnostic criteria that can be readily translated into general clinical practice to improve the diagnostic rate of PCM. In fact, these criteria are currently used to define eligibility to receive social support from the Japanese government for PCM as a rare and intractable disease.

Nevertheless, further research to unravel the molecular pathogenesis and develop effective therapeutic modalities is warranted. Nationwide registry research on PCM is currently ongoing in Japan with the aim of better understanding the disease burden as well as the unmet needs of this life-threatening disease with poor therapeutic options.

Secondary Causes of Hypertriglyceridemia are Prevalent Among Patients Presenting With Hypertriglyceridemia Induced Acute Pancreatitis

BACKGROUND

Hypertriglyceridemia induced acute pancreatitis (HIAP) is the third common cause of acute pancreatitis. HIAP can result in recurrent attacks of severe AP with significant morbidity and mortality. Hypertriglyceridemia (HTG) could be primary or secondary. Although genetic causes of HTG are well studied, the prevalence of secondary causes of HTG in patients presenting with HIAP is not well characterized. This study aimed to identify the prevalence of risk factors for secondary hypertriglyceridemia among patients presenting with HIAP in a tertiary referral center in a large metropolitan area.

METHODS

This is a retrospective analysis of all patients admitted with AP from August 2012-2017. A subgroup of patients with triglycerides >880 mg/dl were included for analysis. Secondary causes of HTG were identified. Secondary analysis evaluating the severity of pancreatitis was performed.

RESULTS

There were 3,746 patients admitted for AP of which 57 patients had AP and HTG. Of these 57 patients, 70.2% had history of diabetes mellitus, 26.3% had history of heavy alcohol use, 22.8% had chronic kidney disease, 47.3% with obesity, and 21.1% with metabolic syndrome. Two patients were classified as unexplained HTG. Secondary analysis showed a total of 45.6% of patients requiring ICU admission. 26.3% of patients with severe inflammatory pancreatitis and 17.5% of patients with severe necrotizing pancreatitis.

CONCLUSIONS

In our cohort of HIAP, 55 out of 57 patients had secondary causes for HTG. Identifying secondary causes of HTG during acute hospitalization is important to tailor outpatient treatment in order to prevent future admissions with HIAP.

Gene expression profiles of recurrent acute pancreatitis risk in patients with sustained chylomicronemia

A fasting triglyceridemia >10 mmol/L is associated with chylomicronemia (CM) and an increased recurrent acute pancreatitis (RAP) risk. The number of pancreatitis episodes varies significantly between patients with CM. The objective of this study was to investigate gene expression profiles of RAP in patients with CM. A total of 47 CM subjects participated in this study. Prior to the analyses, all patients were divided into three groups covering a wide spectrum of RAP: 0 (n = 21), 1-3 (n = 10) or >4 (n = 16) pancreatitis episodes. Gene expression profiles were compared to those of 15 healthy normolipidemic controls. Differential expression moderated T-tests between studied groups were performed using a linear model of the Bioconductor package Limma. The False discovery rate was controlled using the Benjamini-Hochberg procedure. At a p-value <0.01, a false discovery rate of 5% and a >2-fold change expression significance levels, a set of 41 probes have been found differentially expressed in CM subjects with no pancreatitis, 103 in the CM group with 1 to 3 pancreatitis, and 94 in the group with ≥4 pancreatitis compared to healthy controls. Of the identified annotated probes, 14 are shared by all CM groups; 3 are specific to CM with no pancreatitis; 11 are specific to CM with 1 to 3 pancreatitis, and 17 are specific to CM with ≥4 pancreatitis. Most of the annotated biomarkers are involved in inflammatory, immune, lipoprotein kinetics or signalling biological pathways. These results reveal gene expression signatures of RAP in patients with CM.

Dissection of Clinical and Gene Expression Signatures of Familial versus Multifactorial Chylomicronemia

Familial chylomicronemia syndrome (FCS) is a rare disorder associated with chylomicronemia (CM) and an increased risk of pancreatitis. Most individuals with CM do not have FCS but exhibit multifactorial CM (MCM), which differs from FCS in terms of risk and disease management. This study aimed to investigate clinical and gene expression profiles of FCS and MCM patients. Anthropometrics, clinical, and biochemical variables were analyzed in 57 FCS and 353 MCM patients. Gene expression analyses were performed in a subsample of 19 FCS, 28 MCM, and 15 normolipidemic controls. Receiver operating characteristic (ROC) curve analyses were performed to analyze the capacity of variables to discriminate FCS from MCM. Sustained fasting triglycerides ≥20 mmol/L (>15 mmol/L with eruptive xanthomas), history of pancreatitis, poor response to fibrates, diagnosis of CM at childhood, body mass index <22 kg/m², and delipidated apolipoprotein B or glycerol levels <0.9 g/L and <0.05 mmol/L, respectively, had an area under the ROC curve ≥0.7. Gene expression analyses identified 142 probes differentially expressed in FCS and 32 in MCM compared with controls. Among them, 13 probes are shared between FCS and MCM; 63 are specific to FCS and 2 to MCM. Most FCS-specific or shared biomarkers are involved in inflammatory, immune, circadian, postprandial metabolism, signaling, docking systems, or receptor-mediated clearance mechanisms. This study reveals differential signatures of FCS and MCM. It opens the door to the identification of key mechanisms of CM expression and potential targets for the development of new treatments.

Familial chylomicronemia syndrome: an under-recognized cause of severe hypertriglyceridaemia

Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive disorder of chylomicron metabolism causing severe elevation of triglyceride (TG) levels (>10 mmol L^-1 ). This condition is associated with a significant risk of recurrent acute pancreatitis (AP). AP caused by hypertriglyceridaemia (HTG) has been associated with a worse prognosis and higher mortality rates compared to pancreatitis of other aetiology. Despite its association with poor quality of life and increased lifelong risk of HTG-AP, few healthcare providers are familiar with FCS. Because this condition is under-recognized, the majority of FCS patients are diagnosed after age 20 often after consulting several physicians. Although other forms of severe HTG such as multifactorial chylomicronemia have been associated with high atherosclerotic cardiovascular disease (ASCVD) risk and metabolic abnormalities, ASCVD and metabolic syndrome are not usually observed in FCS patients. Because FCS is a genetic condition, the optimal diagnosis strategy remains genetic testing. The presence of bi-allelic pathogenic mutations in LPL, APOC2, GPIHBP1, APOA5 or LMF1 genes confirms the diagnosis. However, some cases of FCS caused by autoantibodies against LPL or GPIHBP1 proteins have also been reported. Furthermore, a clinical score for the diagnosis of FCS has been proposed but needs further validation. Available treatment options to lower triglycerides such as fibrates or omega-3 fatty acids are not efficacious in FCS patients. Currently, the cornerstone of treatment remains a lifelong very low-fat diet, which prevents the formation of chylomicrons. Finally, inhibitors of apo C-III and ANGPTL3 are in development and may eventually constitute additional treatment options for FCS patients.

Practical definitions of severe versus familial hypercholesterolaemia and hypertriglyceridaemia for adult clinical practice

Diagnostic scoring systems for familial hypercholesterolaemia and familial chylomicronaemia syndrome often cannot differentiate between adults who have extreme dyslipidaemia based on a simple monogenic cause versus people with a more complex cause involving polygenic factors and an environmental component. This more complex group of patients carries a substantial risk of atherosclerotic cardiovascular disease in the case of marked hypercholesterolaemia and pancreatitis in the case of marked hypertriglyceridaemia. Complications are mainly a function of the degree of disturbance in lipid metabolism resulting in elevated lipid levels, so the added value of knowing the precise genetic cause in clinical decision making is unclear and does not lead to clinically meaningful benefit. We propose that for severe elevations of plasma low density lipoprotein cholesterol or triglyceride, the primary factor driving intervention should be the biochemical perturbation rather than the clinical risk score. This underscores the importance of expanding the definition of severe dyslipidaemias and to not rely solely on clinical scoring systems to identify individuals who would benefit from appropriate treatment approaches. We advocate for the use of simple, practical, clinical, and largely biochemically based definitions for severe hypercholesterolaemia (eg, LDL cholesterol >5 mmol/L) and severe hypertriglyceridaemia (triglyceride >10 mmol/L), which complement current definitions of familial hypercholesterolaemia and familial chylomicronaemia syndrome. Irrespective of the precise genetic cause, individuals diagnosed with severe hypercholesterolaemia and severe hypertriglyceridaemia require intensive therapy, including special consideration for new effective but more expensive therapies.

Hypertriglyceridemia-Related Pancreatitis In Patients With Type 2 Diabetes: Links And Risks

Disturbances in glucose and lipid homeostasis are cardinal features of the metabolic syndrome that affect millions of people worldwide. These conditions have multi-organ impact, and while cardiovascular effects are usually the core for studies and preventive measures, other systems may also be affected, including the pancreas. Acute pancreatitis related to severe hypertriglyceridemia is an under-recognized condition that could lead to significant morbidity and mortality. Therefore, when suspected, prompt diagnosis and treatment should be initiated to cover the various aspects of this disorder. Though commonly known to be associated with excess of alcohol use, hypertriglyceridemia-related pancreatitis is particularly observed in diabetics, especially when uncontrolled. Here, we portray the possible mechanisms and clinical features that link type 2 diabetes, hypertriglyceridemia and pancreatitis, and discuss their health-related outcomes and the current and novel treatment options for this unique disease.

Volanesorsen and Triglyceride Levels in Familial Chylomicronemia Syndrome

BACKGROUND

Familial chylomicronemia syndrome is a rare genetic disorder that is caused by loss of lipoprotein lipase activity and characterized by chylomicronemia and recurrent episodes of pancreatitis. There are no effective therapies. In an open-label study of three patients with this syndrome, antisense-mediated inhibition of hepatic APOC3 mRNA with volanesorsen led to decreased plasma apolipoprotein C-III and triglyceride levels.

METHODS

We conducted a phase 3, double-blind, randomized 52-week trial to evaluate the safety and effectiveness of volanesorsen in 66 patients with familial chylomicronemia syndrome. Patients were randomly assigned, in a 1:1 ratio, to receive volanesorsen or placebo. The primary end point was the percentage change in fasting triglyceride levels from baseline to 3 months.

RESULTS

Patients receiving volanesorsen had a decrease in mean plasma apolipoprotein C-III levels from baseline of 25.7 mg per deciliter, corresponding to an 84% decrease at 3 months, whereas patients receiving placebo had an increase in mean plasma apolipoprotein C-III levels from baseline of 1.9 mg per deciliter, corresponding to a 6.1% increase (P<0.001). Patients receiving volanesorsen had a 77% decrease in mean triglyceride levels, corresponding to a mean decrease of 1712 mg per deciliter (19.3 mmol per liter) (95% confidence interval [CI], 1330 to 2094 mg per deciliter [15.0 to 23.6 mmol per liter]), whereas patients receiving placebo had an 18% increase in mean triglyceride levels, corresponding to an increase of 92.0 mg per deciliter (1.0 mmol per liter) (95% CI, -301.0 to 486 mg per deciliter [-3.4 to 5.5 mmol per liter]) (P<0.001). At 3 months, 77% of the patients in the volanesorsen group, as compared with 10% of patients in the placebo group, had triglyceride levels of less than 750 mg per deciliter (8.5 mmol per liter). A total of 20 of 33 patients who received volanesorsen had injection-site reactions, whereas none of the patients who received placebo had such reactions. No patients in the placebo group had platelet counts below 100,000 per microliter, whereas 15 of 33 patients in the volanesorsen group had such levels, including 2 who had levels below 25,000 per microliter. No patient had platelet counts below 50,000 per microliter after enhanced platelet-monitoring began.

CONCLUSIONS

Volanesorsen lowered triglyceride levels to less than 750 mg per deciliter in 77% of patients with familial chylomicronemia syndrome. Thrombocytopenia and injection-site reactions were common adverse events. (Funded by Ionis Pharmaceuticals and Akcea Therapeutics; APPROACH Clinical Trials.gov number, NCT02211209.).

Severe Hypertriglyceridemia-Related Pancreatitis: Characteristics and Predictors of Recurrence

OBJECTIVES

The diagnosis of severe hypertriglyceridemia (HTG) as a cause for acute pancreatitis is often delayed with limited data on the characteristics and predictors of recurrent pancreatitis in this population.

METHODS

A regional database of severe HTG level of 1000 mg/dL or greater was analyzed to identify subjects with acute pancreatitis. Factors associated with recurrent pancreatitis during long-term follow-up were investigated.

RESULTS

Severe HTG-associated pancreatitis was evident in 171 patients (75% diabetics). Recurrent pancreatitis was observed in 16%; this was associated with younger age, alcohol abuse, and an increase in triglyceride levels. In multivariable analysis, peak triglycerides level of greater than 3000 mg/dL (hazard ratio, 2.92; 95% confidence interval, 1.28-6.64; P = 0.011) and most recent triglycerides level of greater than 500 mg/dL (hazard ratio, 3.72; 95% confidence interval, 1.60-8.66; P = 0.002) remained independently associated with recurrent pancreatitis. These lipid measures as well as alcohol abuse were additionally correlated with a stepwise increase in the number of pancreatitis episodes.

CONCLUSIONS

Severe HTG-related pancreatitis was closely associated with diabetes. Extreme HTG and a lack of attainment of lower triglyceride levels were independent long-term predictors of recurrent pancreatitis. These findings emphasize the importance of early identification and successful treatment of severe HTG and its underlying disorders to reduce the burden of recurrent pancreatitis.

Co-occurrence of heterozygous CREB3L3 and APOA5 nonsense variants and polygenic risk in a patient with severe hypertriglyceridemia exacerbated by estrogen administration

We describe a case of a 36-year-old woman with severe hypertriglyceridemia likely caused by double heterozygosity of a known pathogenic APOA5 nonsense variant (p.Q275X) and a novel CREB3L3 nonsense variant (p.C296X) on a background of very strong polygenic susceptibility. Her clinical course worsened with development of eruptive xanthomata after oral administration of 2 mg estradiol twice daily for 2 weeks as part of a medical protocol for intrauterine embryo transfer following in vitro fertilization. Her triglyceride levels decreased to baseline and xanthomata resolved without treatment after discontinuation of hormonal therapy, which also resulted in termination of pregnancy. Before undergoing a second embryo transfer using her natural cycle and no exogenous hormones, the patient started combination therapy with eicosapentaenoic acid ethyl ester and gemfibrozil, leading to an ∼80% decrease in triglyceride levels. She continued treatment throughout pregnancy, which progressed to term with the delivery of healthy twins.

Clinical features and outcomes of severe, very severe, and extreme hypertriglyceridemia in a regional health service

BACKGROUND

Comprehensive data on severe hypertriglyceridemia (HTG) in the general population setting are limited and of importance due to the increase in metabolic risk factors and novel therapies under development.

OBJECTIVE

To investigate contributing causes and outcomes of severe to extreme HTG.

METHODS

Regional database retrospectively analyzed for subjects with severe HTG. Adverse outcomes were investigated in correlation to HTG severity, with follow-up initiating at first documentation of HTG > 1000 mg/dL.

RESULTS

A total of 3091 subjects with severe (peak triglycerides 1000-1999 mg/dL; n = 2590), very severe (2000-2999 mg/dL; n = 369), and extreme (≥3000 mg/dL; n = 132) HTG were identified. Mean age was 48 ± 12 years; 73% males. Obesity (48%) and diabetes (62%) were main contributing factors. During follow-up (median 101 months), 4.7% subjects had pancreatitis, 4.7% myocardial infarction, and 6% stroke. Compared with severe HTG, the multivariate-adjusted hazard ratio for pancreatitis was 3.22 (95% confidence interval 2.21-4.70) for individuals with very severe HTG and 5.55 (3.53-8.71) for those with extreme HTG, P < .0001. In contrast, the extent of HTG severity at these levels was not associated with worse cardiovascular outcomes or death. Most subjects (81%) achieved triglyceride levels <500 mg/dL, associated with lower risk for developing pancreatitis but not myocardial infarction or stroke.

CONCLUSIONS

Severity of HTG is closely related to cardiometabolic conditions, with a stepwise increase in the risk for pancreatitis, particularly if not attaining reduced triglyceride levels during the follow-up. In contrast, whereas mild-to-moderate HTG is a known established cardiovascular risk factor, very severe and extreme HTG may not further increase the risk for myocardial infarction, stroke, or mortality.