Causes, clinical findings and therapeutic options in chylomicronemia syndrome, a special form of hypertriglyceridemia.

The prevalence of hypertriglyceridemia has been increasing worldwide. Attention is drawn to the fact that the frequency of a special hypertriglyceridemia entity, named chylomicronemia syndrome, is variable among its different forms. The monogenic form, termed familial chylomicronemia syndrome, is rare, occuring in 1 in every 1 million persons. On the other hand, the prevalence of the polygenic form of chylomicronemia syndrome is around 1:600. On the basis of the genetical alterations, other factors, such as obesity, alcohol consumption, uncontrolled diabetes mellitus and certain drugs may significantly contribute to the development of the multifactorial form. In this review, we aimed to highlight the recent findings about the clinical and laboratory features, differential diagnosis, as well as the epidemiology of the monogenic and polygenic forms of chylomicronemias. Regarding the therapy, differentiation between the two types of the chylomicronemia syndrome is essential, as well. Thus, proper treatment options of chylomicronemia and hypertriglyceridemia will be also summarized, emphasizing the newest therapeutic approaches, as novel agents may offer solution for the effective treatment of these conditions.

The Chylomicronemia Syndrome Is Most Often Multifactorial: A Narrative Review of Causes and Treatment.

The chylomicronemia syndrome occurs when triglyceride levels are severely elevated (usually >16.95 mmol/L [1500 mg/dL]) and is characterized by such clinical features as abdominal pain, acute pancreatitis, eruptive xanthomas, and lipemia retinalis. It may result from 1 of 3 conditions: the presence of secondary forms of hypertriglyceridemia concurrent with genetic causes of hypertriglyceridemia, termed multifactorial chylomicronemia syndrome (MFCS); a deficiency in the enzyme lipoprotein lipase and some associated proteins, termed familial chylomicronemia syndrome (FCS); or familial partial lipodystrophy. Most chylomicronemia syndrome cases are the result of MFCS; FCS is very rare. In all these conditions, triglyceride-rich lipoproteins accumulate because of impaired plasma clearance. This review describes the 3 major causes of the chylomicronemia syndrome; their consequences; and the approaches to treatment, which differ considerably by group.

Clinical, biochemical and molecular analysis of two infants with familial chylomicronemia syndrome.

Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive disease due mainly to inherited deficiencies in the proteins or enzymes involved in the clearance of triglycerides from circulation. It usually happens in late childhood and adolescence, which can have serious consequences if misdiagnosed or untreated. In the present study, we investigated two Chinese male babies (A and B), 30d and 48d in age, respectively, who have milky plasma. Clinical, biochemical, and radiological assessments were performed, while samples from the patients were referred for molecular diagnosis, including genetic testing and subsequent analysis of related genes. The fasting serum lipids of the two patients showed extreme lipid abnormalities. Through a low-lipid formula diet including skimmed milk and dietary advice, their plasma lipid levels were significantly lower and more stable at the time of hospital discharge. The genetic testing revealed compound heterozygote mutations in the lipoprotein lipase (LPL) gene for patient A and two known compound heterozygote LPL gene mutations for the patient B. FCS is the most dramatic example of severe hypertriglyceridemia. Early diagnosis and timely dietary intervention is very important for affected children.

10-Year Comparative Follow-up of Familial versus Multifactorial Chylomicronemia Syndromes.

CONTEXT: The relative incidence of acute pancreatitis, ischemic cardiovascular disease, and diabetes in hyperchylomicronemic patients exhibiting familial chylomicronemia syndrome (FCS) or multifactorial chylomicronemia syndrome (MCS) is unknown. OBJECTIVE: The objective was to study the occurrence of these events in FCS and MCS patients compared with the general population. METHODS: Twenty-nine FCS and 124 MCS patients, with genetic diagnosis, in 4 lipid clinics were matched with 413 controls. Individual hospital data linked to the national claims database were collected between 2006 and 2016. The occurrence of complications was retrospectively assessed before follow-up and during a median follow-up time of 9.8 years, for 1500 patient years of follow-up. RESULTS: Patients with FCS were younger than those with MCS (34.3 ±â€…13.6 vs 45.2 ±â€…12.6 years, P < 0.01). During the study period, 58.6% of the FCS patients versus 19.4% of the MCS patients had at least 1 episode of acute hypertriglyceridemic pancreatitis (AHP) (hazard ratio [HR] = 3.6; P < 0.01). Conversely, the ischemic risk was lower in FCS than in MCS (HR = 0.3; P = 0.05). The risk of venous thrombosis was similar in both groups. The incidence of diabetes was high in both groups compared with matched controls (odds ratio [OR] = 22.8; P < 0.01 in FCS and OR = 30.3; P < 0.01 in MCS). CONCLUSION: The incidence of AHP was much higher in FCS than in MCS patients, whereas the incidence of ischemic cardiovascular events was found to be increased in MCS versus FCS patients and a representative matched control group. Differences in both triglyceride-rich lipoproteins metabolism and comorbidities in MCS versus FCS drive the occurrence of different patterns of complications.

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.

GPIHBP1 autoantibody syndrome during interferon ß1a treatment.

BACKGROUND: Autoantibodies against glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) cause chylomicronemia by blocking the ability of GPIHBP1 to bind lipoprotein lipase (LPL) and transport the enzyme to its site of action in the capillary lumen. OBJECTIVE: A patient with multiple sclerosis developed chylomicronemia during interferon (IFN) ß1a therapy. The chylomicronemia resolved when the IFN ß1a therapy was discontinued. Here, we sought to determine whether the drug-induced chylomicronemia was caused by GPIHBP1 autoantibodies. METHODS: We tested plasma samples collected during and after IFN ß1a therapy for GPIHBP1 autoantibodies (by western blotting and with enzyme-linked immunosorbent assays). We also tested whether the patient's plasma blocked the binding of LPL to GPIHBP1 on GPIHBP1-expressing cells. RESULTS: During IFN ß1a therapy, the plasma contained GPIHBP1 autoantibodies, and those autoantibodies blocked GPIHBP1's ability to bind LPL. Thus, the chylomicronemia was because of the GPIHBP1 autoantibody syndrome. Consistent with that diagnosis, the plasma levels of GPIHBP1 and LPL were very low. After IFN ß1a therapy was stopped, the plasma triglyceride levels returned to normal, and GPIHBP1 autoantibodies were undetectable. CONCLUSION: The appearance of GPIHBP1 autoantibodies during IFN ß1a therapy caused chylomicronemia. The GPIHBP1 autoantibodies disappeared when the IFN ß1a therapy was stopped, and the plasma triglyceride levels fell within the normal range.

Encephalopathy in type I hyperlipidemia.

Familial chylomicronemia syndrome is a group of rare genetic disorders characterized by deficient activity of an enzyme lipoprotein lipase or apo-protein C-II deficiency. In this paper we present an infant with massive hyperchylomicronemia and severe pancreatitis. Exchange transfusion for controlling hypertriglyceridemia and pancreatitis led to an increase in hyperviscosity which resulted in encephalopathy.

Familial type I hyperlipoproteinemia caused by apolipoprotein C-II deficiency.

A study was made on the clinical and biochemical features of siblings of patients with hyperchylomicronemia and its inherited relationship. It was not a case of the classical type of familial LPL deficiency, but of familial apolipoprotein C-II deficiency. The first patient with apolipoprotein C-II deficiency was reported by Breckenridge et al. and our patients provide the basis for the second report of this new disease. Our observations in this study strongly suggest that familial apolipoprotein C-II deficiency is transmitted by an autosomal recessive mode of inheritance and heterozygotes of this disorder have no abnormalities of plasma lipid and lipoproteins in spite of the reduced plasma apolipoprotein C-II.

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

Type I hyperlipoproteinemia (type I HLP) is a rare disorder of lipid metabolism characterized by fasting chylomicronemia and reduced postheparin plasma lipoprotein lipase (LPL) activity. Most cases of type I HLP are due to genetic defects in the LPL gene or in its activator, the apolipoprotein CII gene. Several cases of acquired type I HLP have also been described in the course of autoimmune diseases due to the presence of circulating inhibitors of LPL. Here we report a case of type I HLP due to a transient defect of LPL activity during puberty associated with chronic idiopathic urticaria (CIU). The absence of any circulating LPL inhibitor in plasma during the disease was demonstrated. The LPL genotype showed that the patient was heterozygous for the D9N variant. This mutation, previously described, can explain only minor defects in the LPL activity. The presence of HLP just after the onset of CIU, and the elevation of the LPL activity with remission of the HLP when the patient recovered from CIU, indicate that type I HLP was caused by CIU. In summary, we report a new etiology for type I HLP - a transient decrease in LPL activity associated with CIU and with absence of circulating inhibitors. This is the first description of this association, which suggests a new mechanism for type I HLP.

Treatment of primary chylomicronemia due to familial hypertriglyceridemia by omega-3 fatty acids.

Primary familial forms of chylomicronemia can lead to acute life-threatening complications, especially acute pancreatitis. The main aim of therapy is to avoid this so-called chylomicronemia syndrome. In 12 patients with primary chylomicronemia due to familial hypertriglyceridemia, the addition of 2.16 g omega-3 fatty acids over 4 weeks and 4.32 g for 8 weeks resulted in a decrease of serum triglyceride levels from 1,624 +/- 333 to 894 +/- 241 mg/dL after 12 weeks. Cholesterol and triglyceride levels in the chylomicron fraction were reduced concomitantly, the apolipoprotein B-100/B-48 ratio increased, very--low-density lipoprotein (VLDL) triglycerides, VLDL cholesterol, and total cholesterol levels decreased, and low-density lipoprotein (LDL) cholesterol showed a tendency to increase, but this finding did not reach significance. High-density lipoprotein (HDL) cholesterol levels remained unchanged, as did the levels of apolipoproteins A-I, A-II, and E, and lipoprotein(a). Apolipoprotein B levels decreased significantly. The decrease of triglyceride levels to still-elevated concentrations was accompanied by a substantial decrease in plasma and whole-blood viscosity and erythrocyte aggregation, which reached normal values. As in chylomicronemia, complications usually occur at triglyceride levels higher than 1,500 mg/dL; patients can still profit from treatment with omega-3 fatty acids, even though triglyceride levels are still substantially elevated. No clinically relevant side effects occurred, with the exception of the manifestation of diabetes mellitus in one patient, which could be reversed after discontinuation of treatment.

Hyperchylomicronaemia due to lipoprotein lipase deficiency as a cause of false-positive newborn screening for biotinidase deficiency.

Two cases of molecular genetically proven lipoprotein lipase deficiency are reported. Both patients were detected owing to a false-positive neonatal screening test for biotinidase deficiency. We conclude that both the fluorimetric and the colorimetric screening tests for biotinidase deficiency used with dried blood samples are affected by severe hyperchylomicronaemia and that, most probably, severe plasma turbidity interferes with the assay.

The molecular defects in lipoprotein lipase deficient patients.

The underlying molecular defects that lead to a deficiency of lipoprotein lipase in two patients from different kindreds presenting with the familial hyperchylomicronemia syndrome have been identified. Sequence analysis of amplified LPL cDNA of the patient from the Bethesda kindred revealed a single point mutation (G to A) at position 781 of the normal gene that resulted in the substitution of an alanine for a threonine at residue 176 and the loss of an SfaN1 site present in the normal LPL gene. Amplification of patient cDNA by the PCR followed by restriction enzyme digestion with SfaN1 established that the patient is a true homozygote for the defect. The proband from the second kindred was found to be a compound heterozygote for two separate allelic mutations, including a T to C transition at nucleotide 836 and a G to A mutation at base 983 that led to the substitution of Ile194 by Thr and Arg243 by His, respectively. Transient expression of the mutant LPL cDNAs from both kindreds in human embryonal kidney-293 cells resulted in the synthesis of enzymatically inactive proteins, establishing the functional significance of the mutations.

Plasma lipoprotein disorders in childhood.

Disturbances of the plasma lipoproteins occur as a secondary manifestation in many diseases and usually resolve with treatment of the underlying condition. Of the inherited primary disorders familial hypercholesterolaemia is the most common and important, carries a high risk for premature coronary heart disease in adults, and should be diagnosed and treated in childhood.