Background: Childhood hypoplastic anemia of unknown etiology had not existed until now. To assess pathophysiological differentiation in childhood hypoplastic anemia, we analyzed red cell membrane components in six children with hypoplastic anemia of unknown etiology.
Methods: The six children all had chronic moderate anemia and thrombocytopenia. They also showed hypoplastic marrow cellularity with erythroblastopenia, megakaryocytopenia, and mild morphological anomalies (pelger Hëut anomaly of neutrophils and bi- or trinuclear erythroblasts), except for one child who had normal platelets and megakaryocytes. Red blood cells of patients and several anemic children, cord blood and healthy controls were analyzed by the peanut lectin agglutination (PNA) test, flow cytometry, sodium dodecyl sulfate_polyacrylamide gel electrophoresis of membrane proteins, high performance liquid chromatography (HPLC) of sugar chains and the colony-forming assay of bone marrow erythroblasts.
Results: In the six children, the PNA agglutination test showed a persistent positive reaction not only for peripheral red blood cells but also for bone marrow erythroblasts. This was not observed in other anemic children and healthy controls. With HPLC analysis, the sugar chains of red blood cell membranes showed the loss of sialic acid from O-linked oligosaccharides.
Conclusions: Our results suggested that the abnormality of red blood cells from these patients was attributable to abnormal surface sugar chains (loss of sialic acid from O-glycan), which are already present at the erythroblast stage in the bone marrow and that may be responsible for a group of anemias.