Identification of a GATA1 mutation causing severe fetal anemia. (A) The proband’s blood smear contains macrothrombocytes (black arrow). (B-D) Representative bone marrow smears show Cabot rings (B; ∗), megaloblasts (C; #), and mitosis (D; +), indicative of megaloblastic anemia. Smears were stained with May-Grünwald and photographed with a Nikon Eclipse E600 microscope equipped with a 100×/0.30 numerical aperture oil-immersion lens and a ProgRes SpeedXT core 5 camera, using Gryphax software (version 2.0). (E) Hemoglobin levels over time; red arrows indicate the time points of red blood cell transfusions. (F) DNA from the affected boy and the unaffected mother and father; the base mutation is indicated by the red arrow. (G) Pedigree of the family; the filled square represents the hemizygous male.