The project was undertaking by Qilu Hospital of Shandong University in China. In order to report the efficacy and safety of vitamin D combining with high-dose dexamethasone for the treatment of adults with newly-diagnosed primary immune thrombocytopenia (ITP).

The investigators anticipate to undertaking a prospective, multicenter, randomised controlled trial of 60 ITP adult patients. One part of the participants are randomly selected to receive vitamin D (given Rocaltrol orally at a dose of 0.25 μg per day for 1 month), combining with dexamethasone (given orally at a dose of 40 mg per day for 4 days, two-cycles with an interval of 10 days); the others are selected to receive high-dose of dexamethasone treatment plus placebo. Platelet count, bleeding and other symptoms were evaluated before and after treatment. Serum calcium and creatinine are monitored. Adverse events are also recorded throughout the study. In order to report the efficacy and safety of vitamin D combining with high-dose dexamethasone therapy for the treatment of adults with ITP.

Inclusion Criteria:

1. Corresponding to the diagnostic criteria for immune thrombocytopenia
2. Newly diagnosed ITP patients
3. To show a platelet count <30 * 10^9/L, and with bleeding manifestations
4. Willing and able to sign written informed consent

Exclusion Criteria:

1. Suffered from diseases associated with hypercalcemia.
2. Vitamin D intoxication
3. Received chemotherapy or anticoagulants or other drugs affecting the platelet counts within 3 months before the screening visit;
4. Received second-line ITP-specific treatments (eg, cyclophosphamide, 6-mercaptopurine, vincristine, vinblastine, etc) within 3 months before the screening visit; 3.Received high-dose steroids or IVIG in the 3 weeks prior to the start of the study;
5. Current HIV infection;
6. Severe medical condition (lung, hepatic or renal disorder) other than chronic 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)
7. Female patients who are nursing or pregnant, who may be pregnant, or who contemplate pregnancy during the study period;
8. 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;
9. Patients who are deemed unsuitable for the study by the investigator.