The project was undertaking by Qilu Hospital of Shandong University and other 18 well-known hospitals in China. In order to report the efficacy and safety of decitabine combining with dexamethasone for the treatment of adults with immune thrombocytopenia (ITP), compared to dexamethasone alone .

The investigators anticipate to undertaking a parallel group, multicentre, randomised controlled trial of 200 ITP adult patients from 19 medical centers in China. One part of the participants are randomly selected to receive dexamethasone (given 40mg/d for 4 consecutive days as a cycle , If platelet count remained below 30 × 109/L or there were bleeding symptoms by day 10, an additional cycle of dexamethasone was given) combining with decitabine (given intravenously at a dose of 3.5mg/m2/d for 4 consecutive days as a cycle and repeated every 2 weeks for 3 cycles), the others are selected to receive dexamethasone therapy(given 40mg/d for 4 consecutive days as a cycle, If platelet count remained below 30 × 109/L or there were bleeding symptoms by day 10, an additional cycle of dexamethasone was given). Platelet count, bleeding and other symptoms were evaluated before and after treatment, adverse events are also recorded throughout the study in order to report the efficacy and safety of the combination therapy compared to dexemathasone alone therapy for the treatment of adults with ITP.

Inclusion Criteria:

1. Meet the diagnostic criteria for immune thrombocytopenia.
2. within 3 months fromdiagnosis,untreated patients, may be male or female, between the ages of 18 ~ 80 years.
3. To show a platelet count < 30×10^9/L, and with bleeding manifestations.
4. Eastern Cooperative Oncology Group（ECOG）performance status ≤ 2.

Exclusion Criteria:

1. Received chemotherapy or anticoagulants or other drugs affecting the platelet counts within 3 months before the screening visit.
2. Received high-dose steroids or intravenous immunoglobulin transfusion(IVIG) in the 3 weeks prior to the start of the study.
3. Current HIV infection or hepatitis B virus or hepatitis C virus infections.
4. Severe medical condition (lung, hepatic or renal disorder) other than ITP. Unstable or uncontrolled disease or condition related to or impacting cardiac function (e.g., unstable angina, congestive heart failure, uncontrolled hypertension or cardiac arrhythmia)
5. Female patients who are nursing or pregnant, who may be pregnant, or who contemplate pregnancy during the study period.
6. Have a known diagnosis of other autoimmune diseases, established in the medical history and laboratory findings with positive results for the determination of antinuclear antibodies, anti-cardiolipin antibodies, lupus anticoagulant or direct Coombs test.
7. Patients who are deemed unsuitable for the study by the investigator.