Familial hyperlipidemia type 2

Familial hyperlipidemias are classified according to the Fredrickson classification. Type II familial hyperlipidemia is divided into 2 subtypes, IIa and IIb. IIa is linked with mutations in the LDL receptor (LDLR) or genes that regulate the LDL uptake. Therefore, we see an increase of LDL with type IIa familial hyperlipidemia. IIa can be subdived into 4 different types. FHCL1 is caused by direct mutations of the LDLR. This FCHL1 has different phenotypes linked to it which are cause by mutations in APOA2, EPHX2 and GHR. FCHL2 is caused by mutations in APOB, which acts as a ligand for the LDLR. FHCL3 is caused by mutations in PCSK9 which binds to LDLR to inhibit LDL uptake. Lastly, FHCL4 is linked with mutations in LDLRAP1, which stimulates receptor binding. Typ IIB familial hyperlipidemia is known as familial combined hyperlipidemia. This type has shown an increase of both LDL and VLDL. Type IIB can be divided into 3 subtypes. FCHL1 is caused by mutations in USF1 which plays a role in cellular transcription. However, it is unclear how exactly this is linked to the lipid metabolism. HYPLIP2 is caused by mutations in APOB, which is linked to the reduced LDL. APOB is also a primmary apolipoprotein for VLDL. Lastly, FCHL3 is linked to LPL mutations, which is mostly linnked to hydrolizing the VLDL into IDL.

家族性高脂血症根据弗雷德里克森分类进行分类。II型家族性高脂血症分为IIa和IIb两个亚型。IIa型与低密度脂蛋白受体（LDLR）或调节LDL摄取的基因突变有关，因此，在IIa型家族性高脂血症中观察到LDL水平的升高。IIa型可进一步细分为四种不同类型。FHCL1由LDLR的直接突变引起，这种FCHL1与APOA2、EPHX2和GHR基因突变相关的不同表型相关。FCHL2由APOB基因突变引起，APOB作为LDLR的配体。FHCL3由PCSK9基因突变引起，PCSK9与LDLR结合以抑制LDL摄取。最后，FHCL4与LDLRAP1基因突变有关，该突变刺激受体结合。IIB型家族性高脂血症也称为家族性混合性高脂血症。此型表现出LDL和VLDL水平的升高。IIB型可分为三个亚型。FCHL1由USF1基因突变引起，USF1在细胞转录中发挥作用。然而，其与脂质代谢的具体联系尚不清楚。HYPLIP2由APOB基因突变引起，APOB与降低的LDL相关，APOB也是VLDL的主要载脂蛋白。最后，FCHL3与LPL基因突变相关，LPL主要与水解VLDL为IDL有关。