Decay-accelerating factor and CD59 expression in peripheral blood cells in aplastic anaemia and report of a case of paroxysmal nocturnal haemoglobinuria secondary to aplastic anaemia.

Using flow cytometry, decay-accelerating factor (DAF) and CD59 have been measured in peripheral blood cells of 11 patients with aplastic anaemia and 34 healthy controls. Ten of the patients had monophasic fluorescence profiles similar to those of the controls. However, one patient had small DAF- and CD59-negative populations in granulocytes and monocytes, but not in erythrocytes. One year after the first assay, a second flow cytometric study revealed that all peripheral blood cell species, including erythrocytes, contained DAF- and CD59-deficient populations. At this time, a sucrose haemolysis test was positive. This is the first reported case of aplastic anaemia-PNH syndrome in which DAF- and CD59-negative cells appeared first in granulocytes and monocytes and later in all types of peripheral blood cells.