Transfusion anemia.

Vitamin A is a pivotal biochemical factor required for normal proliferation and differentiation as well as for specialized functions, such as vision. The dietary intake of 1500 IU/day is recommended in the first year of life. Here, we report the case of an infant who had been given 62 000 IU/day for 80 days. The infant showed several clinical signs of retinol intoxication, including severe anemia and thrombocytopenia. Bone marrow showed a remarkably reduced number of erythroid and megakaryocytic cells. The interruption of vitamin A treatment was immediately followed by clinical and biochemical recovery. To clarify whether the effects of retinol are due to a direct action on bone marrow cell proliferation, we investigated the activity of retinol (both the drug and the pure molecule) on the growth of K-562, a multipotent hematopoietic cell line, and on bone marrow mesenchymal stem cells. We observed that vitamin A strongly inhibited the proliferation of the cells at concentrations similar to those reached in vivo. Subsequent biochemical analyses of the cell cycle suggested that the effect was mediated by the up-regulation of cyclin-dependent kinase inhibitors, p21(Cip1) and p27(Kip1). These are the first findings to demonstrate that infant hypervitaminosis A causes a severe anemia and thrombocytopenia and that this is probably due to the direct effect of the molecule on the growth of all bone marrow cellular components. Our data also suggest potential bone marrow functional alterations after excessive vitamin A intake because of emerging social habits.

Anemia↗

PubMed2002

Role of HFE in iron metabolism, hereditary haemochromatosis, anaemia of chronic disease, and secondary iron overload.

Hereditary haemochromatosis is an iron overloading disorder caused by common mutations in the HFE gene. However, information with respect to the function of HFE protein does not explain how mutations in HFE lead to hereditary haemochromatosis. We propose a molecular model in which HFE has two mutually exclusive activities in cells: inhibition of uptake or inhibition of release of iron. The balance between serum transferrin saturation and serum transferrin-receptor concentrations determines which of these functions predominates. With this input, HFE enables the intestinal crypt cells and reticuloendothelial system to interpret the body's iron requirements and regulate iron absorption and distribution. In our model, mutations in HFE result in over absorption of dietary iron, and patterns of tissue iron deposition in agreement with clinical observations of hereditary haemochromatosis.

Anemia↗