Keywords: Myelodysplastic syndromes; del(5q); non-del(5q); mutations; lenalidomide EN Myelodysplastic syndromes del(5q) non-del(5q) mutations lenalidomide e133 e137 5 05/19/20 20200515 NES 200515 Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal stem cell disorders characterised by ineffective haematopoiesis leading to peripheral blood cytopenias and an increased risk of transformation to acute myeloid leukaemia (AML) (Haferlach I et al. i , [5]; Makishima I et al. i , [8]). Lenalidomide (LEN) has been approved for the treatment of patients with del(5q) low-risk MDS and transfusion dependence. We collected 74 samples from patients with MDS at diagnosis or treatment-naïve with LEN follow-up treatment of two or more cycles; 32 patients presented with del(5q), while 42 patients did not have del(5q) in their karyotype (Table S1). As expected, responders were mainly classified in MDS with isolated del(5q) (71%), while non-responders were enriched in MDS with ring sideroblasts and with single lineage dysplasia (MDS-RS-SLD; 33%), and MDS with multilineage dysplasia (MDS-MLD; 26%; Table 1). 1 TableClinical characteristics of the patients. [Extracted from the article]