Paroxysmal nocturnal hemoglobinuria and acute non-lymphocytic leukemia. A report of three cases exhibiting different cytologic types.

Three individuals with paroxysmal nocturnal hemoglobinuria (PNH) developed acute non-lymphocytic leukemia (ANLL) as a terminal event. The cytologic types were different in each case suggesting a transformation that may involve a pleuripotent stem cell. Eight previous cases of PNH terminating in acute leukemia have been reported which have also been ANLL in type. Whether PNH should be considered a myelodysplastic or myeloproliferative disorder remains to be seen. PNH has been considered a clonal disorder with several populations of erythrocytes being present. Cytogenetics in the current cases failed to reveal any karyotypic abnormalities during the time PNH was present. However, an abnormal clone appeared in two cases during the time leukemia supervened. Additional studies of PNH as a postulated clonal disorder may provide interesting knowledge for this uncommon disorder.