BCR-FGFR1 MPN is a rare disease that manifests as diverse phenotypes attesting to the proposal that the transforming genetic defect occurs in a pluripotent hematopoietic stem cell capable of multilineage differentiation and further corroborated in the patient described herein whereby initial successful treatment of the presenting acute leukemia revealed the underlying MPN. The gene discussed is FGFR1; the disease is myeloproliferative neoplasm.