The blood of children with severe Mediterranean anemia was found to have a high serum iron and an absence of a latent or unbound iron capacity of the serum. Whereas serum iron levels comprise approximately one third of the total iron-binding capacity in normal children and adults, the two values are equal in the severe form of Mediterranean anemia. The iron-binding capacity of the serum in this condition is therefore fully saturated and quantitatively lower than in normal children.The absence of a measurable latent iron-binding capacity does not depend entirely on the liberation of iron from exogenously administered blood. Comparable changes were also noted in two nonanemic adult carriers possessing the trait of the disease, in two children with the mild form not requiring transfusions, and in one severely anemic child with Mediterranean anemia who had never been transfused. Similar changes occurred in three patients with spherocytic anemia and in five children with sickle cell anemia, one of whom had never been transfused.In every instance therefore of the advanced form of Mediterranean anemia and in some of the nonanemic and mildly anemic forms of this disease, a fully saturated metal-binding protein is present in total amounts usually less than those found in normal children. In contrast, children with iron deficiency anemia manifest a reduction in percentage saturation of iron-binding protein, an increased level of unbound latent iron-binding capacity and a markedly elevated total iron-binding capacity.The failure to demonstrate a latent iron-binding capacity of the serum in asymptomatic persons adds another criterion to those already established for the identification of carriers of the trait of Mediterranean anemia who constitute the source of its transmission.The presence of bilirubin in increased concentrations in the serum of patients with severe Mediterranean anemia does not interfere with its capacity to combine with iron. The capacity for binding iron was restored when Fraction IV-7 was added to samples of icteric sera of patients in whom no capacity had previously been demonstrated.The high serum iron and absence of latent iron-binding capacity observed in children with severe Mediterranean anemia receiving multiple transfusions correspond to the changes regarded as diagnostic of transfusion hemosiderosis and hemochromatosis. While these changes remain unaltered in Mediterranean anemia, their reversibility has been demonstrated in two children with hemophilia who received weekly transfusions of small amounts of blood. Following cessation of this form of therapy a decrease of serum iron and a gradual restoration of iron-binding capacity were noted.
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