Detailed knowledge about differentiation syndrome (DS) has remained limited. There are 2 large studies conducted by the Spanish workgroup PETHEMA (Programa Español de Tratamientos en Hematología; Spanish Program on Hematology Treatments) and the European group trial (LPA 96-99 and APL 93) in which the incidence, characteristics, prognostic factors and outcome of patients developing DS are evaluated. Both have d...