DOI: 10.36347/sjams.2020.v08i03.019

Pages: 897-901

MDS/MPN-RS-T is a clinical-biological entity of haematological malignancies border between myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN), declared in 2016 by WHO as a separate entity of its own unlike old classifications. Its particularity lies in the association of an MDS with ringed sideroblasts (MDS-RS) with a MPN represented in this case by its similarity to an essential thrombocytemia (ET) because of thrombocytosis. Clinically, the association of splenomegaly with chronic "refractory" anemia guides the diagnosis. Cytology is a large-scale orientation tool. It sometimes targets some signs of peripheral dysgranulopoiesis with thrombocytosis and giant platelets. Bone marrow smear shows hyperlobed megakaryocytes (similar as those found in ET or primary myelofibrosis (PMF), sometimes cytoplasmic degranulation of the granular line and often many signs of dyserythropoiesis with more than 15% of ringed sideroblasts (RS) in Prussian blue staining. However, the molecular study retains its full scope to confirm the diagnosis by objectifying the mutation SF1B3 (spliceosome gene) generally found in MDS-RS, accompanied by the mutations found in negative BCR-ABL MPN (JAK2, CAL-R and MPL), thus explaining the hybrid nature of this rare myeloid entity. This genotype can be more complex when associated with other mutations characteristic of MDS (ASXL1, DNMT3A, SETBP1 or TET2) thus worsening the prognosis of patients. We report here a case of a 56-year-old patient followed for ET whose diagnosis was renewed in MDS / MPN-RS-T by cytology and molecular biology.