Primary myelofibrosis (PMF) is a clonal, BCR-ABL1 negative myeloproliferative neoplasm characterised by splenomegaly, leukoerythroblastic peripheral blood picture and bone marrow fibrosis. Different cytogentic abnormalities are documented in PMF which have impact on clinical outcome and overall survival. Del 5q31 is documented in only 0. 8% of PMF patients and is associated with poor outcome and increased risk of progression to acute leukemia. Anemia with del 5q responds frequently to lenalidomide treatment. We are reporting case of a middle-aged male who presented with constitutional symptoms, myelofibrosis; and calreticulin type 2 mutation was present. His cytogenetics showed del 5q positivity. He was started on lenalidomide but developed toxic epidermal necrolysis, resultantly lenalidomide was stopped. Skin eruptions are a known entity in patients with lenalidomide therapy; but to date, there is no reported case of lenalidomide induced toxic epidermal necrolysis (TEN) in patients with myelofibrosis.