Narrative Review: Paroxysmal Nocturnal Hemoglobinuria: The Physiology of Complement-Related Hemolytic Anemia

You are asked to see a 37-year-old male carpenter who wasnoted to be anemic and mildly thrombocytopenic during a routine physical examination. The patient has been married for 11 years and has a 5-year-old son and an 8-year-old daughter. He reports that he has been in good health but has noted increasing fatigue over the past 2 months. Two weeks ago, he and his son had viral gastroenteritis that manifested with nausea and diarrhea. His son recovered within 24 hours, but the patient had burgundy-colored urine that persisted for 2 additional days (Figure 1). On physical examination, the pa-tient is well developed and well nourished, has mildly icteric sclera, and has mild discomfort on deep abdominal palpation but no masses or organomegaly. Complete blood count reveals a leukocyte count of 4.7 109 cells/L with a normal differ-ential, hemoglobin level of 84 g/L, and platelet count of 96 109 cells/L. His absolute reticulocyte count is