Eculizumab in Treating Patients With Paroxysmal Nocturnal Hemoglobinuria

DISEASE CHARACTERISTICS: * Diagnosis of paroxysmal nocturnal hemoglobinuria * Must have required ≥ 4 episodes of transfusions for anemia or anemia-related symptoms within the past year * Mean pre-transfusion hemoglobin ≤ 10. 5 g/dL over the past year * Glycosylphosphatidylinositol (GPI)-deficient red blood cell clone (type III cells) of ≥ 10% by flow cytometry * Must have received 1 packed red blood cell transfusion during the study observation period (within 48 hours of the hemoglobin level that precipitated the transfusion) and within 1.5 g/dL of the mean pre-transfusion hemoglobin level over the past year * Pre-transfusion hemoglobin ≤ 9 g/dL with symptoms * Pre-transfusion hemoglobin ≤ 7 g/dL without symptoms * Received Neisseria meningitidis vaccination at least 2 weeks before initiation of study therapy PATIENT CHARACTERISTICS: Age * 18 and over Performance status * Not specified Life expectancy * Not specified Hematopoietic * See Disease Characteristics * Absolute neutrophil count \> 500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * Lactate dehydrogenase ≥ 1.5 times upper limit of normal Renal * Not specified Immunologic * No known or suspected active bacterial infection * No recurrent bacterial infections * No history of meningococcal disease Other * No known or suspected hereditary complement deficiency * No other condition that would increase the patient's risk or confound the outcome of the study * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy * See Disease Characteristics * No prior bone marrow transplantation * Concurrent epoetin alfa allowed\* Chemotherapy * Not specified Endocrine therapy * Concurrent corticosteroids allowed\*\* Radiotherapy * Not specified Surgery * Not specified Other * More than 30 days since prior participation in another investigational drug trial * More than 30 days since prior investigational agents, devices, or procedures * Concurrent immunosuppressants allowed\* * Concurrent warfarin allowed provided INR level is stable for the past 4 weeks and expected to remain stable during observation and study treatment * Concurrent iron supplements or folic acid allowed\*\* * Concurrent low-molecular weight heparin allowed\*\* NOTE: \*Provided dose is stable for the past 26 weeks and during study observation and treatment NOTE: \*\*Provided dose is stable for the past 4 weeks and expected to remain stable (or decrease for corticosteroids) during study observation and treatment