[Paroxysmal nocturnal hemoglobinuria secondary to an extracorpuscular elutable factor (immunoglobulin)]

A case is reported of Coombs-negative hemolytic anemia in the form of transitory PNH associated with acquired immunohemolytic anemia (AIHA). The patient, a 43-year-old man, was admitted to hospital because of jaundice and hemoglobinuria. Investigations revealed hemolytic anemia with the characteristics of PNH (positive Ham test, 50% hemolysis with the sucrose test) and of AIHA (microspherocytosis, survival of isologous red blood cells t1/2 = 9.5 days). The titer of cold agglutinins was not significant. Pre-incubation of the patient's red blood cells with anti-human F (ab')2 caused marked inhibition of hemolysis during the sucrose test. Isologous red blood cells, pre-incubated with an eluate obtained from the patient's erythrocytes, became sensitive to hemolysis during the sucrose test. The sucrose test is pathognomonic for PHN. The "false" positivity in the present case is possibly due to an immunoglobin conferring on the erythrocytes the characteristic property of PNH cells by blocking the activity of the decay accelerating factor.