APOB and familial hyperaldosteronism: Although historically the prevalence of heterozygous FH (HeFH) is thought to be 1 in 500, recent studies have indicated the prevalence of HeFH in the United Kingdom and in countries in Europe may be twice as high.3, 4, 5 The underlying genetic cause for FH is most often due to mutations within the LDLR gene, which encodes the low-density lipoprotein receptor, but mutations in apolipoprotein B and proprotein convertase subtilisin/kexin type 9 can produce a phenotype identical to LDLR FH.6