UNLABELLED:Pure red cell aplasia (PRCA) is an uncommon disorder, characterized by transfusion dependent anemia, reticulocytopenia with selective aplasia or paucity of erythroid cells in bone marrow. There are only a few large series of PRCA reported in literature. This is the largest single center series of PRCA from India. OBJECTIVE:To evaluate the utility of Immunohistochemistry with Glycophorin A on bone marrow biopsies in quantitating the cut-off percentage of erythroid blasts required for diagnosis, as the upper cut-off percentage of erythroblasts for establishing a diagnosis of PRCA is still not clear. METHODS:The clinical data were obtained from patients' case files. Immunohistochemistry with Glycophorin A was performed using an immunoperoxidase technique and percentage of Glycophorin A positive cells of all nucleated cells was calculated by two independent observers. RESULTS:In our study, bone marrow aspirates showed a variable percentage of erythroblasts ranging from 2 to 12% (mean 6.3%) in children and from 1 to 8% (mean 4.6%) in adults on Giemsa smears. Immunohistochemistry (IHC) with Glycophorin A showed a mean positive cell % of 8.2 (range 2-16%) and 6.8 (1-9%) in pediatric and adult respectively against a mean of 28% (range 21-39%) in idiopathic thrombocytopenia (ITP) cases. Treatment with prednisone showed good response in a majority of both adults and childhood PRCA. Cyclosporine was found to be a good alternative in prednisone non-responders. Thymectomy was beneficial in patients with thymoma. CONCLUSION:A higher percentage of erythroid cells (>5%) does not exclude a diagnosis of PRCA in an appropriate clinical setting and therefore can be managed as PRCA.