Hemoglobin J-Chicago (beta76(E20) Ala yields Asp): a new hemoglobin variant resulting from substitution of an external residue.

An electrophoretically fast-moving hemoglobin variant was found in a 2-yr-old boy who was referred for evaluation with findings of iron deficiency anemia. The anemia was corrected, and no hematologic abnormality remained after treatment with iron. Oxygen affinity of the blood was normal, and no evidence was found of instability of the variant hemoglobin. Structural studies demonstrated a substitution of aspartic acid for alanine at beta76 (E20). This change did not appear to cause any functional disruption of the hemoglobin in this patient, as would be predicted by the position of the affected animo acid residue on the surface of the molecule.