Patient blood and bone marrow histopathology. (A-F) Human data for brother (A,C,E) and sister (B,D,F). Similar results were observed for both siblings. The patient samples shown were obtained before the patients had ever received hematopoietic growth factors and at a time when there was no evidence of active infection. (A-B) Patient peripheral blood smears. (A) Giant platelets (arrow) and vacuolization of monocytes. (B) Rare but morphologically normal neutrophils in the blood. (C-F) Patient bone marrow smears. (C-D) All stages of myeloid differentiation through an abundance of morphologically mature neutrophils are evident. (E) Vacuolization of 2 metamyelocytes. A majority of megakaryocytes were monocytoid (mean, 68%) and frequently (12%) demonstrated penetration by intact cells (emperipolesis) that appeared to be neutrophils (arrow). (G-H) Mouse data in the absence of G-CSF or AMD3100. (G) G6pc3^−/− mouse peripheral blood. Morphologically mature neutrophils were evident. (H) G6pc3^−/− mouse bone marrow. An abundance of mature neutrophils is evident.