447 Transformation of Polycythemia Vera to Acute Erythroid Leukemia: An Extremely Rare Case Emphasizing Diagnostic and Molecular Vigilance

Introduction/Objective Acute erythroid leukemia (AEL) is a rare (<1%) and highly aggressive subtype of acute myeloid leukemia (AML), characterized by predominant erythroid precursor proliferation. The 2022 WHO defines AEL as a distinct entity, whereas the ICC includes it under AML with mutated TP53. AEL frequently harbors complex karyotypes and biallelic TP53 alterations, and exhibits marked chemoresistance. The transformation from polycythemia vera (PV) to PEL is exceedingly rare, with only very few cases described in the literature with absence of prior radiation or alkylator exposure. Methods/Case Report We report a 71-year-old woman with a 8-year history of JAK2 V617F-mutated PV, treated with hydroxyurea and phlebotomy, who developed anemia, thrombocytopenia, and 50% circulating blasts. Bone marrow biopsy revealed 70% CD34-positive blasts, fibrosis, and a complex monosomal karyotype. Molecular testing showed JAK2 and TP53 mutations. Despite treatment with azacytidine and venetoclax, her disease progressed. Repeat marrow showed >30% proerythroblasts positive for CD71, CD117, and E-cadherin, consistent with AEL. Results NA Conclusion This case illustrates the rare evolution of PV to AEL in the absence of prior chemotherapy and highlights the need for comprehensive morphologic and molecular assessment in high-risk PV. Early recognition of AEL is critical due to its poor prognosis and limited therapeutic options.