A 12 months old girl of ajabi pal aped pallor since 3 months of age. One unit of bloth ansfusion was done at 5 months of age. Now presents with pallor, on examination hepatosplenomegaly. Hemoglobin was 3.8 gm/d1., MCV= 68, MCH = 19. Peripheral smear showed schistocytes. Bone marrow examination show erythroid hyperplasia. Diagnosis is: