Study of Safety in Hemolytic Paroxysmal Nocturnal Hemoglobinuria (PNH) Patients Treated With Eculizumab

Inclusion Criteria: * PNH \> 6 months * Type III PNH red blood cell (RBC) clone by flow cytometry \>10% * At least one transfusion in the past 2 years but no more than 3 transfusions in the past 12 months; or personal beliefs that preclude the use of transfusion with severe hemolytic PNH * Lactate dehydrogenase (LDH) \>1.5 x upper limit of normal * Must avoid conception * Willing and able to give written informed consent Exclusion Criteria: * Platelet count of \<30,000/mm3 * Absolute neutrophil count \<500/ul * Active bacterial infection * Hereditary complement deficiency * History of bone marrow transplantation * Participation in any other investigational drug trial or exposure to other investigational agent, device or procedure within 30 days * Pregnant, breast-feeding, or intending to conceive * History of meningococcal disease