Relative erythroid hyperplasia in the bone marrow at diagnosis of aplastic anaemia: a predictive marker for a favourable response to cyclosporine therapy.

Predicting the treatment response of aplastic anaemia (AA) is essential when considering cyclosporine (CyA) therapy among several treatment options, because it requires at least 2 months determine whether the therapy is beneficial to a patient with AA. To identify the characteristics of patients with AA who are likely to respond to CyA therapy we retrospectively reviewed the clinical records and bone marrow smears of patients treated with CyA. Among 30 patients who received the therapy for at least 3 months within 1 year after diagnosis of AA, and who had not been exposed to antilymphocyte or antithymocyte globulin, 16 (53%) responded with disease remission. CyA-responsive patients had a significantly higher ratio of erythroblasts to granulocytes (E/G ratio) in the bone marrow at the time of diagnosis as compared with patients refractory to therapy (P = 0.004). Multivariate analysis revealed that a high E/G ratio ( > 0.6) was significantly associated with a good response to CyA (P = 0.03): 15 (83%) of the 18 patients with an E/G ratio > 0.6 responded, but only one (8%) of the 12 with an E/G ratio > or = 0.6 did. Although the presence of subclinical paroxysmal nocturnal haemoglobinuria was suspected from the relative erythroblastosis observed in the bone marrow of these patients, flow cytometric analysis of neutrophils in the peripheral blood failed to reveal neutrophils deficient for glycosyl-phosphatidylinositol (GPI) anchored membrane proteins in all but one case. Identification of the presence of relative erythroid hyperplasia in he bone marrow when AA is diagnosed may help to predict a favourable response to CyA therapy, and therefore facilitate the selection of optimal therapy for AA.