IBSP and autosomal recessive hypophosphatemic rickets: Mutations identified in the human DMP1 gene that are responsible for ARHR phenotype include (1) p.M1V, (2) c.1483del1490, removing the last 18 amino acid residues, and (3) deletion of 49 kb between DMP1 exon 3 to an intergenic region 5' to integrin-binding sialoprotein.(6,9,29) The first missense mutation of the signal peptide results in abnormal targeting to the cytoplasm, and the third mutation is a functionally null allele with no DMP-1 expression.