abnormal erythrocyte morphology leptocytosis 2010-06-01T03:33:04Z MP:0010175 MPheno.ontology Mexican hat erythrocytes csmith increased Mexican hat cell number increased codocyte number increased target cell number target erythrocytes the presence of unusually thin or flattened red blood cells that when stained show a dark center and a peripheral ring of hemoglobin, separated by a pale unstained ring containing less hemoglobin, resulting in a bull's-eye appearance and resembling a 3D sombrero when viewed under EM; seen in certain anemias, thalassemias, hemoglobinopathies, obstructive jaundice, and the post-splenectomy state wafer-thin erythrocytes