2004). While truncation mutations in the APOB gene cause hypobetalipoproteinemia, mutations causing hypercholesterolemia are due to missense mutations that result in ligand‐defective apoB protein. Defective binding of LDL‐C from an individual with clinical FH, but no LDLR pathogenic variant, was reported in 1987 (Vega and Grundy 1986) and followed shortly by the identification of the genetic defect (Innerarity et al. 1987). This evidence concerns the gene APOB and hypobetalipoproteinemia.