Deficiency of glycosylphosphatidyl inositol‐anchored proteins in patients with aplastic anaemia does not affect response to immunosuppressive therapy

Deficient expression of glycosylphosphatidyl inositol (GPI)‐anchored proteins in aplastic anaemia (AA) patients has previously been reported to be associated with a poor response to immunosuppressive (IS) therapy. Here we report the response to IS therapy of 111 patients with AA and correlate this with GPI‐anchored protein expression on peripheral blood cells by flow cytometry. A GPI‐anchored protein deficient population was identified in 15% (17/111) of patients with AA who had a negative Ham's test and no laboratory evidence of haemolysis. Patients were treated with antilymphocyte globulin and/or cyclosporin A, or oxymetholone. Bone marrow transplantation was performed in 12 patients, seven of whom had not responded to IS therapy. In patients tested for GPI‐anchored protein expression prior to IS therapy there was no difference in response rate to IS therapy between AA patients with a GPI‐anchored protein deficiency and those with normal GPI‐anchored protein expression (50% response rate versus 75%, respectively). Survival in these two groups was similar at 90% with follow‐up over 140 months from diagnosis. Eight of the 17 AA patients who developed a GPI‐anchored protein‐deficient population later went on to develop a positive Ham's test. From this study we demonstrate a lower incidence of GPI‐anchored protein deficiency in AA patients compared with previous reports. In addition we have shown that the presence of a GPI‐anchored protein‐deficient cell population in patients with AA who have a negative Ham's test is not a poor prognostic factor in terms of response and survival after IS therapy.