It is rare to have MDS and PNH coexist as two full blown disorders but PNH clones can be present in MDS and PNH can resemble some features of MDS. Among acquired stem cell disorders, pathological links between myelodysplastic syndromes (MDS) and aplastic anaemia (AA), and paroxysmal nocturnal haemoglobinuria (PNH) and AA, have been often described, whereas the relationship between MDS and PNH is not entirely clear. Many reports identified small PNH clones in other stem cell failure syndromes, such as aplastic anemia or low-risk myelodysplastic syndrome have at least biochemical evidence of hemolysis, but typically the PNH clone is small (< 10%) so that hemolysis does not contribute significantly to the underlying anemia. Using high-sensitivity flow cytometry, approximately 60% of patients with aplastic anemia and 20% of patients with low-risk MDS have been found to have a detectable population of GPI-AP–deficient erythrocytes and granulocytes. In these cases, the focus of treatment is on the BM failure component of the disease. Intravascular hemolysis is the dominant feature of classic PNH, and this process is blocked by the complement inhibitor eculizumab(Soliris). When intravascular hemolysis is the predominant feature, treatment should be directed to the PNH component. The large majority of patients with PNH/AA and PNH/MDS have relatively small PNH clones (< 10%) and require no specific PNH therapy; in these cases, treatment should focus on the underlying BM failure syndrome(Parker et al).
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Wang SA, Pozdnyakova O, Jorgensen JL, Medeiros LJ, Stachurski D, Anderson M, Raza A, Woda BA. Detection of paroxysmal nocturnal hemoglobinuria clones in patients with myelodysplastic syndromes and related bone marrow diseases, with emphasis on diagnostic pitfalls and caveats. Haematologica. 2009 Jan; 94(1):29-37.
Young NS. Paroxysmal nocturnal hemoglobinuria and myelodysplastic syndromes: clonal expansion of PIG-A-mutant hematopoietic cells in bone marrow failure.Haematologica. 2009 Jan;94(1):3-7.
Charles J. Parker, Management of Paroxysmal Nocturnal Hemoglobinuria in the Era of Complement Inhibitory Therapy ASH Education Book December 10, 2011 vol. 2011 no. 1 21-29
Fahri Sahin et al, Pesg PNH diagnosis, follow-up and treatment guidelines. Am J Blood Res. 2016; 6(2): 19–27.
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