The severity of the FH phenotype, in addition to CVD risk, may be associated with the combined effect of two pathogenic variations in the two primary candidate genes, LDLR and APOB. The few studies on the double-heterozygous FH cases carrying both LDLR and APOB variants reveal that the clinical phenotype is more severe when compared to the simple heterozygous FDB and ADH forms. The gene discussed is APOB; the disease is familial hyperaldosteronism.