Flow cytometry-detected changes in megaloblastic anemia secondary to cobalamin deficiency.

Introduction: Megaloblastic anemias secondary to Vitamin B12 deficiency are a group of pathologies produced by defective nuclear DNA synthesis.

Objective: To describe the maturation alterations found in hematopoietic precursors of the bone marrow in a series of patients with megaloblastic anemia.

Methods: Were included patients attended at the Regional Hospital of Concepción with bone marrow samples sent for the study of cytopenia by flow cytometry whose final diagnosis was megaloblastic anemia. The immunophenotype was performed with CD45, CD34, CD117, HLA-DR, markers of neutrophil (CD13, CD11b, CD10, CD16) and/or erythroblast (CD105, CD71, CD36) maturation.

Results: From the flow cytometry laboratory database, 8 patients with megaloblastic anemia were identified, and myelodysplastic syndromes (n=9) and normal or reactive bone marrow (n=10) were used as controls. 44% were men, with a median age of 58 years. Megaloblastic anemia was associated with a higher proportion of size and complexity of erythroid and myeloid progenitors compared to lymphocytes compared to controls. The total percentage of erythroblasts and the proportion of CD34+ myeloid cells associated with erythroid lineage was higher in megaloblastic anemia, associated with a maturation arrest in the CD105+ precursor stage (69% vs 19% and 23%, <0.001). The heterogeneity of CD36 and CD71 in megaloblastic anemia was similar to myelodysplastic syndromes.

Conclusions: Megaloblastic anemia produces a heterogeneous involvement of hematopoiesis, characterized by a greater size and cellular complexity of precursors of the neutrophil and erythroid series and a maturation arrest of the erythroblasts.