Immune thrombocytopenic purpra(ITP) is an autoimmune thrombocytopenic syndrome characterized by decreased platelet count and increased risk of bleeding, primarily due to immunoglobulins G(IgG)autoantibodies opsonizing the individual's platelets,resulting in markedly enhanced Fc receptors(FcR)-mediated phagocytosis and destruction by macrophages in the reticuloendothelial system within spleen Severe ITP defined as :Patients who have clinically relevant bleeding that mean that patients have bleeding symptoms at presentation sufficient to mandate treatment,or occurrence of new bleeding symptoms requiring additional therapeutic intervention with a different platelet-enhancing agent or an increased dose.Prednislone is the standard intial first-line therapy in naïve ITP patients.Prednislone is usually given at 0.5 to 2mg/kg until platelet count increase(>30-50 *10^9/L )which may require several days to several weeks,however prednisone should be rapidly tapered after 4 weeks to avoid corticosteroid related complication. In a trial to shorten the duration and reduce adverse effects of corticosteroids treatment. Dexamethasone in a dose of 40mg/day has been administered for 4days (equivalent to~400mg of prednisone per day) achieved 85% initial reponse and sustained response 50% of adult cases of ITP at 6 months follow up