Evolution of paroxysmal nocturnal hemoglobinuria clon during an hemolitic crisis in a patient with aplastic anemia. Flow cytometry analysis.

Evolution of paroxysmal nocturnal hemoglobinuria clon during an hemolitic c risis in a patient with aplastic anemia. Flow cytometry analysis. The expan sion of paroxysmal nocturnal hemoglobinuria (PHN) clone was evaluated in a patient with aplastic anemia (AA) of 18 years of evolution during an hemoly tic crisis. On day 0, Ham and Sucrosa tests wore positive and hematological parameters were altered. Low hemoglobin (Hb) levels and erythrocyte and le ukocyte counts were found and continued decreasing on days 7 and 24 (last d ay of study). High LDH levels, indirect bilirrubin and reticulocyte counts were detected throughout. We evaluated CD55 and CD59 on erythrocytes by flo w cytometry. Our results showed low CD55 expression with respect to the nor mal pattern. Since day 0, CD59 staining detected two red cell populations: PNH I (48%), cells with positive fluorescence similar to normal and PNH III (52%), negative cells (PNH clone). These negative cells increased, reachin g 70% on day 24. Other membrane anchored leukocyte proteins were also absen t (CD14) or decreased (CD16). We found a good correlation between clinical observations, evolution of the laboratory values and expansion of the PNH c lone.