Myeloproliferative Neoplasm with BCR-FGFR1 Fusion Presenting as Eosinophilic Myeloproliferative Syndrome

Myeloproliferative neoplasms with FGFR1 rearrangements, historically described as the 8p11 myeloproliferative syndrome, represent a rare but highly aggressive group of hematologic disorders driven by constitutive activation of the FGFR1 tyrosine kinase. These neoplasms often manifest with striking eosinophilia and carry a significant risk of progression to acute leukemia. Among the different FGFR1 fusion partners, the BCR-FGFR1 rearrangement is particularly uncommon and portends a challenging clinical course.[1]We describe the case of a middle-aged woman who presented with fatigue, weight loss, and splenomegaly, accompanied by pronounced leukocytosis and eosinophilia. Cytogenetic analysis revealed a t(8;22)(p11;q11) translocation resulting in a BCR-FGFR1 fusion. Despite initial cytoreductive therapy, her disease evolved rapidly, underscoring the aggressive nature of this entity. She ultimately required intensive therapy and consideration for allogeneic stem cell transplantation.This case highlights the diagnostic and therapeutic challenges of BCR-FGFR1–positive neoplasms and emphasizes the importance of early recognition, molecular testing, and timely referral for potentially curative interventions. In the era of emerging FGFR inhibitors, documenting such cases adds valuable insight into the natural history and management strategies for this rare and devastating disorder.