Decitabine has been reported to have a clinically significant, often long lasting effect on the platelet count in myelodysplastic syndromes(MDS). It is also reported that decitabine could increase platelet counts by enhancing megakaryocyte maturation and platelet release. Immune thrombocytopenia(ITP) is known as an immune-mediated acquired disease characterized by transient or persistent decrease of the platelet count. However, refractory ITP is lacking of effective treatments and the efficacy of decitabine in ITP remains poorly understood. Data from this study may provide some idea of decitabine in the treatment of ITP.

The investigators are undertaking a multicenter, single-arm study of primary ITP adult patients from 9 medical centers in China. All the participants are selected to receive low-dose of decitabine treatment (given intravenously at a dose of 3.5mg/m2 for 3 days per cycle for 3 cycles). Platelet count, bleeding and other symptoms were evaluated before and after treatment. Adverse events are also recorded throughout the study.

Inclusion Criteria:

• adult patients with the diagnosis of ITP according to the International Working Group (IWG) guidelines
• failure to splenectomy or at least four standard ITP-specific treatments, but not necessarily undergone splenectomye
• baseline peripheral platelet count less than 30,000/uL or the presence of bleeding symptoms
• need of treatment(s) (including, but not limited to, low dose of corticosteroids) to minimize the risk of clinically significant bleeding. Need of on-demand or

Exclusion Criteria:

• secondary ITP
• pregnancy
• hypertension
• cardiovascular disease
• diabetes
• liver and kidney function impairment
• HCV, HIV, HBsAg seropositive status
• patients with systemic lupus erythematosus and/or antiphospholipid syndrome