Introduction Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder, characterized by the clonal expansion of hematopoietic stem cells lacking glycosylphosphatidylinositol-anchored proteins. PNH clones are frequently found in patients with aplastic anemia (AA), myelodysplastic syndrome (MDS), unusual site thrombosis and non-inmume hemolysis. In Colombia, the DECF laboratory analyses blood samples from all over the country, summited by the APEC (association of patients with complement diseases) for PNH screening. Methods We reviewed the results of flow cytometry (FC) analyses from 1448 patients screened for PNH in DECF laboratory, between 2010 and 2013, and evaluated the association between clinical characteristics and distribution of PNH clone sizes. Clinical characteristics were considered as referred by treating physicians in the FC analysis request forms. All patients included gave written informed consent. Results Mean age of the study population was 44.6±18.5 years and 60.5% were female patients. The most frequent indications for screening were thrombosis (23.5%) and unexplained cytopenias (21.8%). Only 14% of the samples were PNH positive. Table 1 shows the results of FC analysis according to the indications for screening. Median clone sizes were 0.1% (interquartile range (IQR): 0-5.8%) in erythrocytes, 4.2% (IQR: 1.1-53.9%) in granulocytes and 3.8% (IQR: 0.7-64.1%) in monocytes. PNH clone size in granulocytes showed strong correlation with clone size in monocytes (r=0.86, p<0.001) and moderate correlation with clone size in erythrocytes (r=0.65, p=0.001). Figure 1 depicts the distribution of PNH granulocyte clone sizes among indications for screening. In the group of patients with PNH granulocyte clone sizes >5%, those with AA had smaller clone sizes than the rest (Figure 2), while patients with hemolysis showed larger clone sizes than the rest (Figure 3). No significant differences in clone size distribution were found within patients with PNH granulocyte clone sizes ≤5%. Conclusions Our findings are comparable to those reported in other countries. PNH granulocyte clone sizes had stronger correlation with PNH monocyte clones than with PNH erythrocyte clones. About one third of the patients with AA and one fourth of those with hemolysis were PNH positive. Over 50% of patients with AA showed PNH clones sizes <5%. Patients with hemolysis have larger clones than the rest. Further studies are needed to establish the association between PNH clone sizes and clinical outcomes of related disorders. Disclosures: No relevant conflicts of interest to declare.
Objetivo. Describir las características demográficas e inmunofenotípicas de los clones de HPN en pacientes con anemia aplásica.
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