The hematopoietic defect in PNH is not due to defective stroma, but is due to defective progenitor cells.

Although paroxysmal nocturnal hemoglobinuria (PNH) is often associated with aplastic anemia (AA), the nature of the pathogenetic link between PNH and AA remains unclear. Moreover, the PIG-A mutation appears to be necessary but not sufficient for the development of PNH, suggesting other factors are involved. The ability of PNH marrow cells to form in vitro hematopoietic colonies and the ability of PNH marrow to generate stroma that could support hematopoiesis of normal or PNH marrow in cross culture were investigated.