Is Nature Truly Healing Itself? Spontaneous Remissions and Clonal Replacement in Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is considered to be curable only through the means of allogeneic HSCT. One of the many fascinating and scientifically instructive aspects of the pathogenesis of this disease is the rare possibility of its spontaneous remission with disappearance of PNH clone and abatement of clinical symptoms, which has always captivated the research community. Due to the orphan nature of the condition, no clinical predictors have been identified so far as harbingers of this phenomenon. In a classical scenario, exhaustion of PNH clone may be associated with reappearance of aplastic anemia (AA), in which PNH clone reflects a semi-maladaptive attempt of recovery. Consequently, one could stipulate that the retraction of PNH clone(s) would have to be associated with a compensatory re-expansion of normal hematopoiesis should normal counts be maintained. The recent insights into the AA/PNH pathobiology shed light onto molecular underpinnings of polyclonal vs oligoclonal hematopoiesis and their dynamics. Here, through application of NGS we attempted to better discern the mechanism of PNH spontaneous remission taking advantage of our internal cohort of PNH patients.