One of the most common mutations implicated in the development of familial hypertriglyceridemia is a heterozygous inactivating mutation of the LPL gene. Inactivation of this gene leads to an individuals inability to hydrolyze the triglycerides within the VLDL core. This inactivation of function leads to a considerable accumulation of triglycerides and VLDL in the bloodstream, which then contributes to several avenues of pathology. Individuals with insulin resistance can have even further elevated levels of hypertriglyceridemia due to the fact that insulin is a potent activator of LPL. Therefore, an individual who is resistant to the bioactivity of insulin will have decreased LPL activity and will therefore lead to further hypertriglyceridemia, helping push serum triglycerides to pathologic levels. Beyond the classic understanding of single-gene mutation leading to disease, hypertriglyceridemia is also linked to several different genetic loci permitting additional aberrant changes to other lipid levels in the body. Epidemiology
Familial hypertriglyceridemia can follow an autosomal dominant monogenic inheritance pattern. The frequency of heterozygous carriers of certain pathologic mutations in the LPL gene can range from 0.06% to 20%. It is important to note that dissimilar mutations can confer varying degrees of underlying pathology. However, most cases of familial hypertriglyceridemia follow a polygenic inheritance pattern involving mutations in multiple genetic foci. Pathophysiology
Inactivity of lipoprotein lipase (LPL) plays the predominant role in the development of familial hypertriglyceridemia. LPL plays a role in the metabolism of triglycerides within VLDL molecules. Inactivation mutations in LPL will create an environment with an increased concentration of VLDL molecules and therefore, triglycerides.
Familial hypertriglyceridemia (type IV familial dyslipidemia) is a genetic disorder characterized by the liver overproducing very-low-density lipoproteins (VLDL). As a result, an affected individual will have an excessive number of VLDL and triglycerides on a lipid profile. This genetic disorder usually follows an autosomal dominant inheritance pattern. The disorder presents clinically in patients with mild to moderate elevations in triglyceride levels. Familial hypertriglyceridemia is typically associated with other co-morbid conditions such as hypertension, obesity, and hyperglycemia. Individuals with the disorder are mostly heterozygous in an inactivating mutation of the gene encoding for lipoprotein lipase (LPL). This sole mutation can markedly elevate serum triglyceride levels. However, when combined with other medications or pathologies it can further elevate serum triglyceride levels to pathologic levels. Substantial increases in serum triglyceride levels can lead to certain clinical signs and the development of acute pancreatitis. Familial hypertriglyceridemia falls in the Fredrickson-Levy and Lees (FLL) phenotypes. The phenotypes include types I, IIa, IIb, III, IV, and V dyslipidemias. Familial hypertriglyceridemia is considered a type IV familial dyslipidemia it is distinguished from other dyslipidemias based on the individuals lipid profile. Familial hypertriglyceridemia separates itself from other dyslipidemias with significantly high triglycerides and low HDL levels. It is important to recognize that co-morbid conditions that often concomitantly exist with the disorder can further alter the lipid panel. Etiology
Familial hypertriglyceridemia is considered to be inherited in an autosomal dominant manner. However, it is important to recognize that most cases have a polygenic inheritance distancing themselves from traditional Mendelian inheritance patterns.