Adducin-null RBCs show features of HS. (A) RBC volume and hemoglobin concentration histograms indicate a population of small (left-shifted volume histogram) and dehydrated (right-shifted hemoglobin concentration histogram) in α-adducin–null (−/−, bottom) versus wild-type (+/+, top) RBCs. (B) Peripheral blood smears reveal a significant population of spherocytes () with a small population of severely hypochromic cells (). +/+ indicates wild-type; +/−, heterozygotes; and −/−, homozygous null. Bar represents 10 μM. (C) Biconcave RBCs from a normal littermate and (D) an α-adducin–null mouse showing significant spherocytosis. Bar represents 10 μM.