The rituximab could be an alternative to the splenectomy because of its great frequency of effectiveness and its good tolerance in the short and medium term. None the medicamentous treatments usually suggested in alternative to the splenectomy (disulone, danazol, immunosuppressors) indeed makes it possible to obtain an answer prolonged after the stop of therapeutic in a significant number of cases. Moreover, the use of the immunosuppressors such as the cyclophosphamide, the azathioprine or the ciclosporine appears contestable at this stage of the disease because of potential severity their side effects.The primary endpoint is satisfactory response to one year, defined by a figure of plates >=50x109/L and at least 2 times superior in the initial, and persistent figure without treatment during one year after the stop of the treatment by rituximab. Secondary objectives are incomplete response to one year, defined by a figure of platelets >= 30x109/L and < 50x109/L and at least twice the figure initial or > 50x109/L but lower than twice the persistent initial figure without treatment during one year after the end of the treatment by rituximab. Splenectomy at one year satisfactory Response to 2 years incomplete Response to 2 years Splenectomies at 2 years Tolerance of the treatment.