Immunophenotype of myeloid granulocytes: a pilot study for distinguishing myelodysplastic syndrome and aplastic anemia by flow cytometry

It is often difficult to distinguish myelodysplastic syndrome (MDS) from aplastic anemia (AA) because of the considerable clinical, cytologic histologic similarities between these two disorders; however, distinguishing between AA and MDS is of great importance because there is a higher risk of progression to acute leukemia in patients with MDS compared with AA. Up to now, CD34⁺ cells in MDS and AA patients have been studied extensively; however, little information is available on myeloid granulocytes. The aim of this study was to determine whether immunophenotype of myeloid granulocytes in AA patients was different from that of MDS. Flow cytometry was used to assess the immunophenotype of myeloid granulocytes in 22 patients with MDS, 12 with AA, and 10 normal subjects. Our data showed that the percentages of CD13⁺ granulocytes, CD33⁺ granulocytes, CD34⁺ granulocytes, and HLA-DR⁺ granulocytes were significantly higher in patients with MDS than in AA patients and normal subjects (P < 0.05). The percentages of CD15⁺ granulocytes and CD10⁺ granulocytes were significantly lower in patients with MDS than in AA patients and normal subjects (P < 0.05). There were no significant differences in the expression of these markers between patients with AA and normal subjects (P > 0.05). As refractory anemia progressing to refractory anemia with excess blasts, the percentages of CD13⁺ granulocytes, CD33⁺ granulocytes, CD34⁺ granulocytes and HLA-DR⁺ granulocytes were significantly increased, whereas, the percentage of CD15⁺ granulocytes was significantly decreased (P < 0.05). These data suggest that immunophenotype of myeloid granulocytes may be a useful parameter for the differential diagnosis of MDS and AA.