Non-interventional Study of Lenalidomide in the Clinical Routine Treatment of TD Patients With IPSS Low or Int-1 MDS and Isolated Del(5q)

Inclusion Criteria: * Are ≥ 18 years old at the time of signing the Informed consent form (ICF) * Are transfusion dependent or have an history of transfusion dependence; for the purpose of the current Myelodysplastic syndromes (MDS) Post-authorization safety study (PASS), transfusion-dependence is defined as requiring ≥2 RBC units over an 8 week period prior to the date of signature on the ICF (due to MDS-related causes and not because of hemorrhage, trauma, or other acute cause) * Are on active treatment with lenalidomide (Lenalidomide Cohort) or have never been exposed to lenalidomide at the time of signing the ICF (Background Cohort) * Have confirmed diagnosis of IPSS low or intermediate-1-risk MDS with isolated del (5q) (with morphological and cytogenetic information) diagnosed on 15 June 2007 (date of Revlimid first approved in Europe) or later Exclusion Criteria: * Refuse to participate in the Myelodysplastic syndromes (MDS) Post-authorization safety study (PASS), * Are currently participating in an interventional therapeutic clinical trial for MDS (except for erythropoiesis-stimulating agents \[ESAs\] and granulocyte colonystimulating growth factors) * Receive any investigational agent the time of signing the ICF * Have previously been treated with lenalidomide and are no longer on active treatment with lenalidomide at the time of signing the ICF