Osmotic deformability patterns of red blood cells are shown for: (A) Two patients with defined molecular disorders leading to spherocytosis (see Results); (B) Seven patients who present typical characteristics of hereditary spherocytosis, but for whom the molecular disorder is unknown; (C) Two patients with defined molecular disorders leading to elliptocytosis (see Results); (D) Five patients of the same family with defined molecular disorders leading to elliptocytosis or poikilocytosis (see Results); and (E) Three patients who present typical characteristics of hereditary elliptocytosis, but for whom the molecular disorder is unknown. In all graphs, the normal range of osmotic deformability curves is shown (±1 standard deviation [SD]), as well as one typical normal curve (Control).