Investigation of hereditary spherocytosis red blood cell shapes. Three patients diagnosed with hereditary spherocytosis caused by different mutations (panels A–C) showed a spherocyte count of 11% (A), 8% (B), and 10% (C) in their stained peripheral blood smears, as exemplified in panel A (arrows, objective-magnification 100x). Comparison with 3D-rendered confocal recordings (objective-magnification 60x) of glutaraldehyde fixed and CellMask stained cells, however, demonstrated a different percentage of “true spherocytes”: 2.5% (A), 0% (B), and 0.08% (C). They are visualized in the dark colored boxes, each showing one cell from three perpendicular directions and mostly reflecting the amount observed in healthy subjects (0–0.3%, examined in 15 donors). In contrast, many cells look like spherocytes from one direction (leftmost view in all boxes) but the other faces reveal different morphologies, such as mushroom-shaped cells, stomatocytes or other irregular-shaped cells (all light colored boxes) representing “pseudo spherocytes.” These observations could be confirmed in 10 hereditary spherocytosis patients after 3D-imaging of about 1,000 cells per subject. This Figure is a reprint of Simionato et al. (2021).