Rituximab and Prednisone as First-Line Therapy in Treating Patients With Immune Thrombocytopenic Purpura

DISEASE CHARACTERISTICS: * Diagnosis of immune thrombocytopenic purpura (ITP) * Diagnosis must be made according to American Society of Hematology diagnostic guidelines by a member of Mayo Rochester's Division of Hematology/Oncology within the past year * ITP must be confirmed by bone marrow aspiration and biopsy in all patients ≥ 60 years of age\* * Bone marrow studies performed outside Mayo must be reviewed by a Mayo hematopathologist to confirm diagnosis and exclude evidence of other hematologic disorders NOTE: \*Bone marrow evaluation is discretionary for all other patients * Requires treatment, as defined by 1 of the following parameters: * Platelet count ≤ 30,000/mm³ * Platelet count ≤ 50,000/mm³ with episodic bleeding (i.e., spontaneous or with minimal trauma) requiring treatment * No concurrent diagnosis of a condition known to cause secondary immune (or nonimmune) thrombocytopenia, including, but not limited to, any of the following: * Rheumatological conditions, such as lupus, rheumatoid arthritis, scleroderma, or mixed connective tissue disorder * Patients with positive serologies and no concurrent, clinically evident condition are eligible * HIV positive or AIDS * Non-Hodgkin's lymphoma, Hodgkin's lymphoma, chronic lymphocytic lymphoma, multiple myeloma, or other malignant hematological conditions * Clinically evident antiphospholipid antibody syndrome\* or heparin-induced thrombocytopenia * Clinically overt liver disease, hepatitis B surface antigen positive, hepatitis C serology positive, or evidence of a microangiopathic hemolytic anemia, such as disseminated intravascular coagulation, hemolytic-uremic syndrome, thrombotic thrombocytopenic purpura, or preeclampsia NOTE: \*Positive laboratory tests without the defined clinical criteria for a diagnosis of antiphospholipid antibody syndrome is allowed PATIENT CHARACTERISTICS: * ECOG performance status 0-2 * Creatinine ≤ 2 times upper limit of normal (ULN) * Direct bilirubin ≤ 1.5 times ULN * Total bilirubin ≤ 1.5 times ULN * AST ≤ 2.5 times ULN * Hemoglobin ≥ 10 g/dL * WBC ≥ 3,000/mm³ * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No hypersensitivity to murine or chimeric proteins * No other disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the patient at high risk for treatment complications * Able to take a proton-pump inhibitor while on corticosteroids * No unresolved or incompletely treated infection within the past 14 days PRIOR CONCURRENT THERAPY: * No prior corticosteroid therapy since the diagnosis of ITP * Corticosteroid therapy is allowed for up to 14 days prior to study entry, once the baseline CBC has been established * No prior rituximab * No other concurrent therapy for ITP, including androgens, IV immunoglobulins, RH\_o (D) immune globulin, cyclosporine, or azathioprine sodium