Two new human DMT1 gene mutations in a patient with microcytic anemia, low ferritinemia, and liver iron overload.

DMT1 mediates the pH-dependent uptake of Fe(2+) from the diet in duodenal enterocytes and in most other cells. It transfers iron from the endosomes to the cytosol following the uptake of the transferrin-transferrin receptor complex. DMT1 mutations are responsible for severe hypochromic microcytic anemia in rodents and in 2 human patients described recently. We report a compound heterozygote for 2 new DMT1 mutations, associated with microcytic anemia from birth and progressive liver iron overload. The first mutation is a GTG deletion in exon 5, leading to the V114 in-frame deletion in transmembrane domain 2, and the second is a G --> T substitution in exon 8 leading to the G212V replacement in transmembrane domain 5. Together with the 2 previously reported cases, this patient defines a new syndrome of congenital microcytic hypochromic anemia, poorly responsive to oral iron treatment, with liver iron overload associated paradoxically with normal to moderately elevated serum ferritin levels.