Successful treatment of chronic refractory pure red cell aplasia with antithymocyte globulin: Correlation with in vitro erythroid culture studies

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Abstract
Two contrasting cases of chronic refractory pure red cell aplasia (PRCA) responsive to a commercial preparation of horse antihuman thymocyte globulin (ATG) are reported. Both cases were refractory to trials of cyclophosphamide, corticosteroids, and plasmapheresis. One patient developed a reticulocytosis after a single intravenous infusion of ATG; the other patient responded after administration of 14.7 g of ATG over a 28‐day course. At presentation, erythroid progenitors (CFU‐E and BFU‐E) in one patient were normal; in the second patient, the number of erythroid progenitors was severely reduced. Neither patient had a serum IgG inhibitor to progenitor cells as judged by in vitro erythroid colony studies. Both patients had increased numbers of marrow T‐cells and co‐culture studies in one case were consistent with T‐cell‐mediated suppression of erythropoiesis. These studies confirm that ATG is a useful agent in the treatment of refractory PRCA. However, ATG may not act by removal of T suppressor cells in all cases.