In this study we want to investigate if combination therapy with rituximab (R) + dexamethasone (DXM) is superior to monotherapy with DXM in patients with newly diagnosed idiopathic thrombocytopenic purpura (ITP). Before treatment molecular studies - gene expression profiling - are performed to characterize at the molecular level those patients responding adequately to the treatment as compared to those obtaining a minor or no responses.

The hypothesis is that combination therapy is superior to monotherapy as defined above. Using gene expression studies up-front the hypothesis is that this method may be able to predict the response to treatment.

Inclusion Criteria:

• Age 18 years or over
• Diagnosis = ITP + platelet count above or equal to 25 Mia/l or platelet count above or equal to 50 Mia/l and bleeding from the mucous membranes.
• Adequate contraceptive measures within the last 3 months for women of childbearing potential.

Exclusion Criteria:

• Performance status above or equal to 2
• Previous treatment with rituximab
• Immunosuppressive treatment within the last month except for not previously treated patients
• Other serious disease
• Pregnant women and nursing mothers
• Contraindication for rituximab treatment.
• Active infection requiring antibiotic treatment.