Another mutant isoform seen in patients with familial hypobetalipoproteinemia, APOB87Padova, is caused by a single nucleotide deletion at the 5' end of exon 28, leading to a shortened isoform comprising the N-terminal 3968 residues of APOB plus a divergent C-terminal 37 amino acid sequence. This evidence concerns the gene APOB and hypobetalipoproteinemia.