In this prospective and retrospective chart review, investigators will evaluate the response rates and duration of response for patients with relapsed and refractory idiopathic thrombocytopenic purpura (ITP) who have been treated with rituximab and repeated courses of dexamethasone. Investigators will also evaluate observed toxicities of the combination, and characteristics associated with response.

Patients with idiopathic thrombocytopenic purpura (ITP) usually respond with an increase in platelet count after treatment with steroids, but most patients will experience recurrence.Rituximab has been a useful treatment for patients with recurrent ITP; many hundreds of patients have been treated. 30-40% of patients will achieve a complete remission (CR: platelet count >150 x 109/l) with initial treatment. However, most patients will relapse between 1 and 3 years from initial treatment suggesting that long-term "cures" only occur in 20% of the initial patients. An increased rate of durable CRs is therefore a desirable goal. One approach would be to use rituximab maintenance; however, this strategy results in long term B cell suppression. Dexamethasone has also been used to achieve "cure" in ITP, especially in adults at or near diagnosis. An initial study suggested that approximately 50% of patients would achieve a long-term response with only one 4-day cycle of high dose (40 mg/day) dexamethasone. A follow up study suggested that 3-4 cycles of dexamethasone would be better than 1 cycle. Finally, a recent publication suggested that rituximab plus one cycle of dexamethasone was superior to dexamethasone alone, with a > 50% CR rate at 6 months. Based on the published activity of rituximab and dexamethasone in this disorder, some patients have received treatment with combined dexamethasone and rituximab. We will review the data of those patients who have received more than one course of dexamethasone together with rituximab for relapsed or refractory ITP in order to determine the response rate, duration of response, toxicity of the combination, and clinical predictors of response in this group.

Inclusion Criteria:

1. Subjects must be diagnosed with ITP.
2. Subjects must be 3 years old or older
3. Subjects must have a platelet count less than 40,000/uL at initiation of treatment regimen or inability to discontinue maintenance treatments such as intravenous immunoglobulin (IVIG), corticosteroids, azathioprine, and/or a thrombopoietin receptor agonist.

Exclusion Criteria:

1. Subjects who have not been diagnosed with ITP. 2 Subjects who are younger than 3 years old 3. Subjects who have a medical condition that would be adversely affected by high dose steroids

Patients who have received more than one course of dexamethasone together with rituximab for relapsed or refractory ITP.