An unusual case of heterozygous hemoglobin S/hemoglobin Fannin-Lubbock misidentified by capillary hemoglobin electrophoresis

A 58-year-old Hispanic man under treatment for a gangrenous toe was found to have chronic microcytic anemia and a positive sickle cell screen. High-performance liquid chromatography and isoelectric focusing electrophoresis showed that the patient is double heterozygous for hemoglobin S and hemoglobin Fannin-Lubbock. The patient does not have any manifestations of a sickling disorder. Capillary hemoglobin electrophoresis initially misclassified this unusual combination of hemoglobin variants.