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Paroxysmal nocturnal hemoglobinuria: an acquired X-linked genetic disease with somatic-cell mosaicism
1University of Genova Scientific Director Istituto Toscano Tumori, Via Taddeo Alderotti 26N, 50139 Firenze, Italy. lucio.luzzatto@unige.it
Paroxysmal nocturnal hemoglobinuria (PNH) is a severe hemolytic anemia caused by an intrinsic abnormality of the red blood cells that makes them exceedingly susceptible to the lytic action of activated complement (C). This abnormality results from a mutation in the PIG-A gene on Xp22. Given that the mutation is not inherited but is somatically acquired by a hematopoietic stem cell, it creates two populations of blood cells: normal cells and PNH cells. The clinical expression of PNH depends on the relative and absolute expansion of the PNH cell population, which probably depends, in turn, on a paradoxical growth advantage conferred to it by the existence in the patients of an autoimmune process that exerts negative selection against the 'normal' hematopoietic stem cells.
Paroxysmal nocturnal hemoglobinuria (PNH) is a severe hemolytic anemia caused by an intrinsic abnormality of the red blood cells that makes them exceedingly susceptible to the lytic action of activated complement (C). This abnormality results from a mutation in the PIG-A gene on Xp22. Given that the mutation is not inherited but is somatically acquired by a hematopoietic stem cell, it creates two populations of blood cells: normal cells and PNH cells. The clinical expression of PNH depends on the relative and absolute expansion of the PNH cell population, which probably depends, in turn, on a paradoxical growth advantage conferred to it by the existence in the patients of an autoimmune process that exerts negative selection against the 'normal' hematopoietic stem cells.
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