Our understanding of the molecular and biochemical disturbances which characterize nutritional anemias has advanced at a remarkable pace. A relatively new entity is pyridoxine-responsive anemia. In Vilter's1 review of pyridoxine in 1955, the role of vitamin B6 in erythropoiesis in man was entirely unknown. Interest still centered around its requirement in infant nutrition and its ability to alleviate the neuropathy caused by isoniazid therapy. Since the first description in 1956 by Harris et al.2 of spontaneous pyridoxineresponsive anemia (PRA), reports have appeared in the literature with increasing frequency.
Observations to date show that the disease is restricted to erythropoiesis and is characterized generally by a severe anemia. Morphologically, there is hypochromia and microcytosis, accompanied by hyperferremia and hemosiderosis of the reticuloendothelial tissues. Hemoglobin may be restored to normal by pyridoxine administration, but the microcytosis and hypochromia persist. Thus, there is a residual defect which is not correctable by