Familial chylomicronemia syndrome: A comprehensive clinical and genetic approach

Abstract The familial chylomicronemia syndrome (FCS) is characterized by very high levels of circulating triglycerides. FCS is caused by lipoprotein lipase (LPL) deficiency resulting from homozygous or biallelic loss-of-function variants in the LPL or other related genes. Here, we report a case of severe hypertriglyceridemia refractory to conventional therapy in a male patient diagnosed at 33 years of age. LPL activity was below 20%. During the clinical course, the patient developed severe acute pancreatitis in addition to other complications. Two heterozygous variants (c.984G>A and c.1139+6T>C) which had not been previously reported in the major databases were identified in the LPL gene. Treatment with volanesorsen was proposed based on its approved indication as an adjunct to diet in adult patients with confirmed FCS and at high risk for pancreatitis. Volanesorsen was effective and well-tolerated, and the patient did not experience abdominal pain or any other manifestations. The assessment of genetic characterization is essential to guide treatment decisions during follow-up, in addition to the patient's history, their comorbidities and clinical stigmas.

Quilomicronemia familiar / Familial chylomicronemia

Resumen La quilomicronemia familiar es una condición en que una mutación genética altera la capacidad de metabolizar los triglicéridos que viajan en las lipoproteínas, causando elevación extrema de triglicéridos plasmáticos y complicaciones asociadas. La complicación más frecuente es la pancreatitis, que puede llevar a falla multiorgánica o insuficiencia pancreática. La quilomicronemia familiar también afecta la calidad de vida, las relaciones sociales y el desarrollo profesional. El gen más frecuentemente afectado en la quilomicronemia familiar es el de lipoproteína lipasa-1 (LPL), enzima que hidroliza triglicéridos circulantes para su captación tisular. Mutaciones en genes (como APOC2, APOAV, LMF-1, GPIHBP-1) que codifican para proteínas que regulan la maduración, transporte o polimerización de lipoproteína lipasa-1, también pueden estar involucradas. Sin embargo, en cerca del 30% de los pacientes no se encuentra la variante causal. La quilomicronemia familiar debe sospecharse en casos de hipertrigliceridemia extrema, resistente al tratamiento convencional, o que se acompaña de xantomas eruptivos, lipemia retinalis o dolor abdominal. La disponibilidad de escalas de riesgo y pruebas genéticas deben promover la detección oportuna. La nutrición se basa en una dieta muy baja en grasa con adecuada suplencia de vitaminas liposolubles y ácidos grasos esenciales, además de evitar el consumo de alcohol. Si bien el tratamiento farmacológico incluye fibratos y ácidos grasos omega 3, el enfoque actual privilegia agentes biotecnológicos dirigidos a los defectos moleculares propios de la enfermedad. Ello incluye un oligonucleótido antisentido dirigido contra apoC-III (volanesorsen), un anticuerpo monoclonal contra la proteína similar a angiopoietina tipo 3 (evinacumab), y otros compuestos en desarrollo.

Abstract Familial chylomicronemia is a disease in which a genetic mutation affects the ability of the organism to metabolize triglycerides bound to lipoproteins, causing extremely high plasma triglycerides and associated consequences. The most frequent complication is acute pancreatitis, which may lead to multiorganic failure or pancreatic insufficiency. Familial chylomicronemia also exerts a profound negative impact on quality of life, social relationships and professional development. The gene most frequently affected is lipoprotein lipase-1 gene (LPL), the enzyme in charge of hydrolyzing circulating triglycerides for tissue uptake. Mutations in other genes regulating maturation, transport or polymerization (eg. APOC2, APOAV, LMF-1, GPIHBP-1) of lipoprotein lipase-1, may also be involved. However, in about 30% of patients the causal variant is not identified. Familial chylomicronemia should be suspected in patients with severe hypertriglyceridemia with poor response to conventional treatment, or accompanied by eruptive xanthomas, lipemia retinalis or abdominal pain. The availability of risk scores and genetic tests should facilitate its opportune detection and management. Nutritional therapy is based on a very-low-fat diet with adequate supply of lipid-soluble vitamins and essential fatty acids, plus avoidance of alcohol consumption. Current pharmacological treatment may include fibrates and omega-3 fatty acids but prioritizes biotechnological agents targeting the molecular disturbances of the disease. These include an antisense oligonucleotide against apoC-III (volanesorsen), a monoclonal antibody against angiopoietin-like protein-3 (evinacumab), and other agents currently in development.

Triglyceride-Rich Lipoproteins and Novel Targets for Anti-atherosclerotic Therapy

Although elevated serum low-density lipoprotein-cholesterol (LDL-C) is without any doubts accepted as an important risk factor for cardiovascular disease (CVD), the role of elevated triglycerides (TGs)-rich lipoproteins as an independent risk factor has until recently been quite controversial. Recent data strongly suggest that elevated TG-rich lipoproteins are an independent risk factor for CVD and that therapeutic targeting of them could possibly provide further benefit in reducing CVD morbidity, events and mortality, apart from LDL-C lowering. Today elevated TGs are treated with lifestyle interventions, and with fibrates which could be combined with omega-3 fatty acids. There are also some new drugs. Volanesorsen, is an antisense oligonucleotid that inhibits the production of the Apo C-III which is crucial in regulating TGs metabolism because it inhibits lipoprotein lipase (LPL) and hepatic lipase activity but also hepatic uptake of TGs-rich particles. Evinacumab is a monoclonal antibody against angiopoietin-like protein 3 (ANGPTL3) and it seems that it can substantially lower elevated TGs levels because ANGPTL3 also regulates TGs metabolism. Pemafibrate is a selective peroxisome proliferator-activated receptor alpha modulator which also decreases TGs, and improves other lipid parameters. It seems that it also has some other possible antiatherogenic effects. Alipogene tiparvovec is a nonreplicating adeno-associated viral vector that delivers copies of the LPL gene to muscle tissue which accelerates the clearance of TG-rich lipoproteins thus decreasing extremely high TGs levels. Pradigastat is a novel diacylglycerol acyltransferase 1 inhibitor which substantially reduces extremely high TGs levels and appears to be promising in treatment of the rare familial chylomicronemia syndrome.