en Pediatric Hematology & Oncology Pediatric Hematology & Oncology پژوهشي Original Article Background: Myelodysplastic syndrome is a mixed clonal disorder of bone marrow progenitor cells. Understanding the pattern of the different lineage-specific, immature, and mature markers in myelodysplastic syndrome will help in setting-up the frame of reference to diagnose. Patients and Methods: We compared 60 bone marrow samples from 30 newly-diagnosed patients with myelodysplastic syndrome and 30 patients with idiopathic thrombocytopenic purpura as the control to perform a quantitative analysis of the antigen expression patterns in granulocytic, monocytic, erythroid and lymphoid lineages and myeloid precursors. Results: Quantitative analysis of CD markers, showed that the mean percentages of CD33, CD13, CD11b, HLA-DR, CD10 and CD34 positive granulocytes were 91%, 84.98%, 77.20%, 14.59%, 40.34% and 34.25%, respectively in myelodysplastic syndrome and 96.89%, 91.57%, 81.47%, 10.56%, 58.30% and 32.37%, respectively in idiopathic thrombocytopenic purpura. Flow cytometric analysis of erythroid lineage showed the mean percentage of CD71 in myelodysplastic syndrome and idiopathic thrombocytopenic purpura cases to be 64.54% and 83%, respectively. Investigation of antigen expression in the myeloid precursors of myelodysplastic syndrome patients showed the mean proportions of: 19.89%, 59.53%, 57.26%, 69.24%, 60.64% and 23.43% for CD117, CD34, HLA-DR, CD33, CD13 and CD11b, respectively. Also, idiopathic thrombocytopenic purpura cases showed the mean percentages of 11.73%, 45.67%, 58.90%, 74.28%, 70.16% and 15.66% for CD117, CD34, HLA-DR, CD33, CD13 and CD11b, respectively. Conclusion: There is no doubt that providing the reference values for an antigen expression pattern among myelodysplastic syndrome cases enhances the utility of flow cytometric analysis interpretation among these patients. Keywords: Myelodysplastic syndromes, flow cytometry, immunophenotyping, antigen expression. Myelodysplastic syndromes, flow cytometry, immunophenotyping, antigen expression 19 26 http://ijbc.ir/browse.php?a_code=A-10-1-56&slc_lang=en&sid=1 Mohadeseh Hashem Boroojerdi 10031947532846002430 10031947532846002430 Yes Nasibeh Daneshvar 10031947532846002431 10031947532846002431 No Peyman Ghoraishizadeh 10031947532846002432 10031947532846002432 No Rajesh Ramasamy 10031947532846002433 10031947532846002433 No Seman Zainina 10031947532846002434 10031947532846002434 No Noor Sabariah 10031947532846002435 10031947532846002435 No