MEDizzy - A 42-year-old man has had multiple episodes of painful red

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Combined Hematology II

A 42-year-old man has had multiple episodes of painful red nodules on his skin from dermal venous thrombosis, as well as abdominal pain from mesenteric vein thrombosis over the past year. He notes passing darker urine. Laboratory studies show Hgb 9.4 g/dL, Hct 29.2%, MCV 100 fL, platelet count 215,000/microliter, and WBC count of 8800/microliter. His RBCs show increased sensitivity to complement lysis. Flow cytometry is most likely to show reduction in which of the following markers on his RBCs?

ExplanationD. This patient is having anemia, hemoglobinuria with mesenteric vein thrombosis which is highly suggestive of PNH, so the option is d. Hemolysis in PNH results from the increased susceptibility of PNH erythrocytes to complement mediated lysis, due to a reduction, or absence, of two important GPI-anchored complement regulatory membrane proteins CD55 and CD59. Thrombosis—the leading cause of death in PNH—occurs in up to 40% of patients. Venous thrombosis in PNH can occur anywhere, with the abdominal veins (hepatic, portal, splenic, and mesenteric) and the cerebral veins being the most common sites. Patients with a large PNH cell population (60% of granulocytes) seem to be at greatest risk for thrombosis. The Ham test and the sucrose hemolysis test (sugar water test) were two of the first assays used to diagnosis PNH. Both assays are performed on erythrocytes and discriminate PNH cells from normal cells on the basis of their greater sensitivity to the hemolytic action of complments. These assays are relatively insensitive and nonspecific. Flow cytometric analysis of granulocytes is the best way to diagnose PNH.