Survival and significance of PNH erythrocytes: a scanning study

The SEM study of PNH erthrocytes which survived incubations with decreasing dilutions (from 1:640 to 1:20) of fresh compatible serum in isotonic sucrose has indirectly evidenced that spherocytes and spherostomatocytes are the most sensitive population to the complement lytic action; swelling is an osmotic consequence of their membrane hypersusceptibility. In such functional abnormality the swollen red cells are closely followed by the cribrous and pitted erythrocytes. A relationship has been found between percentage of the swollen cells and frequency of PNH haemolytic bouts: these are most likely to occur when spherocytes and spherostomatocytes are above 40% of cells. On the contrary, SEM evaluation of swollen erthrocytes does not allow to express any longer-term prognosis about the severity and the course of PNH, owing to the constantly variable marrow production of abnormal erythrocytes.