Identification of a 4-base deletion in the gene in inherited intrinsic factor deficiency

A 4-base deletion has been identified in the coding region of the gene for gastric intrinsic factor (IF) in an 11-year-old girl with severe anemia and cobalamin (Cbl) deficiency. The bone marrow showed frank megaloblastic morphology, and the Schilling test indicated a failure to absorb Cbl that was corrected by coadministration of IF. Pentagastrin administration induced acid secretion, but the gastric juice lacked IF as determined by Cbl binding, by fractionation of protein-bound Cbl, and by immunoprecipitation with anti-IF antiserum. Individual exons were amplified by the polymerase chain reaction by using primers to the flanking intronic regions, and the nucleoticle sequence analysis identified a 4-base deletion (c183_186delGAAT) spanning positions 104 to 107 in exon 2, resulting in premature termination of translation. This mutation also eliminates a site for BstXI endonuclease and introduces a site for BsaBI for identifying this deletion in hereditary IF deficiency.