Successful treatment of refractory/relapsed acquired pure red cell aplasia with sirolimus.

Acquired pure red cell aplasia (aPRCA) is a kind of anemia characterized by severe reticulocytopenia and obvious bone marrow erythroblastic cells decreased. Some patients are refractory or intolerant to the first-line therapy (cyclosporine A with/without steroids). The effects of the second-line therapy are not satisfactory and sometimes not available. In this study, we analyzed the efficacy and side effect of sirolimus on refractory/relapsed aPRCA and investigated the possible mechanism of sirolimus on immune regulation. Twenty-one patients with refractory/relapsed aPRCA were enrolled in this study and were administered with sirolimus. Totally, 76.2% of patients responded to the sirolimus with 42.9% complete response during the experimental period. The median time for reaction was 4 months. Side effects were tolerable including infections; mild oral mucositis; sinus tachycardia, the increase of creatinine, transaminase, triglyceride, or cholesterol; and thrombocytopenia. Most patients stayed in remission or remained stable during the follow-up period. Early drug withdrawal may lead to quick relapse. Compared with healthy control, Treg levels in patients with aPRCA reduced significantly before sirolimus but recovered after successful treatment. Level of Treg cells correlated with hemoglobin level after effective sirolimus treatment. Thus, sirolimus was effective and tolerable for refractory/relapsed aPRCA. Effective sirolimus treatment may lead to the upregulation of Treg cells which may partly explain the underlying mechanism.