Paroxysmal nocturnal hemoglobinuria (PNH) as a clonal disorder.

1. Clonal theories of disease, particularly progressive clonal growth and selection in tumorogenesis, were briefly cited. 2. Evidence for the clonal nature of PNH was presented. Correlation of red cell hemolysis with (a) G-6-PD type in two female G-6-PD mosaics with PNH and with (b) erythrocyte acetylcholinesterase deficiency, provides strong evidence for the clonal theory of PNH. 3. Possible pitfalls in defining "hidden PNH clones" in other diseases by the use of PNH hemolytic tests were discussed. 4. The potential of PNH as a study model for clonal evolution in human disease was emphasized.