No abstract

Severe congenital neutropenia (Kostmann syndrome) is a disorder that presents in the neonatal period, but predisposes to leukemia later in life. This report describes a 4‐y‐old female with a history of severe congenital neutropenia, who developed a clonal abnormality associated with the translocation (7;21;8) (q32;q22;q22) (AML‐1/ETO). She had circulating peripheral blasts and bone marrow blast counts as high as 64% when she received recombinant granulocyte colony‐stimulating factor (rG‐CSF). Her marrow blasts decreased to 4‐20% when rG‐CSF was discontinued. Fluorescence in situ hybridization analysis was performed on bone marrow cell populations sorted by flow cytometry to determine which cell populations had the AML‐1/ETO translocation. The translocation was found in mature neutrophils and blasts, but not in monocytes, lymphocytes or stem cells. Conclusion: These findings suggest that the translocation occurred in a neutrophil progenitor, past the point in ontogeny where monocytes and neutrophils separate. The techniques described may be useful in understanding lineage relationships and leukemogenesis in other clonal abnormalities associated with myelodysplasia and leukemia.