Myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes: a practical guide to diagnosis and management

Myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) overlap syndromes are a rare group of biologically and clinically connected hematologic malignancies that includes chronic myelomonocytic leukemia (CMML), the most common subtype, as well as atypical chronic myeloid leukemia, MDS/MPN with SF3B1 and thrombocytosis, and MDS/MPN, not otherwise specified. Given their rarity and overlapping clinical features, accurate diagnosis and risk stratification presents a significant challenge. Therapeutic approaches are largely borrowed from either MDS or MPN and the only curative option for appropriate patients is allogeneic stem cell transplantation. Recent advances have started to uncover the pathobiologic basis for these diseases, leading to novel clinical trials for MDS/MPN overlap syndromes, in particular CMML. This review is a practical guide for the diagnosis and management of MDS/MPN overlap syndromes and presents novel therapeutics being specifically designed for these diseases to improve their historically poor outcomes.