Anti-CD20 treatment of relapsed or refractory immune thrombocytopaenic purpura (ITP) after first line corticosteroid treatment

INTERVENTION: All patients will be randomised between: Arm A: conventional dose rituximab 375 mg/m^2, 4 weekly doses Arm B: conventional dose rituximab 375 mg/m^2, 2 weekly + 2 weekly doses, dependent on response Arm C: high dose rituximab 750 mg/m^2, 2 weekly doses CONDITION: Immune thrombocytopaenic purpura (ITP) ; Haematological Disorders ; Purpura and other haemorrhagic conditions PRIMARY OUTCOME: The response (CR/GR/MR/NR) to treatment.; SECONDARY OUTCOME: 1. Need for emergency treatment (platelet count less than 10 or haemorrhagic diathesis, haemorrhage/bleeding defined by grade 3 or 4 according to NCI CTCAE v3.0); 2. Time to treatment failure/relapse INCLUSION CRITERIA: 1. Age minimal 18 years 2. Subjects with relapsed or refractory ITP (fulfilling the diagnostic criteria given in appendix A) and platelet numbers less than 30 x 10^9/l 3. Having completed first line treatment with corticosteroids 4. Written informed consent 5. World Health Organization (WHO) performance status less than or equal to 2