- The discovery of the gene behind a rare form of inherited iron deficiency may provide clues for new treatments of poor iron absorption in the general population, according to a study released Sunday. Lack of iron is the most common of all nutritional deficiencies and the leading cause of anemia, which affects nearly a third of the world's population, according the World Health Organisation. In the developing world, every second pregnant woman and about 40 percent of preschool children are estimated to be anaemic, a condition that contributes to 20 percent of all maternal deaths.