FGFR1 and acute leukemia: 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.