Rheumatoid arthritis and pure red cell aplasia

Three patients with severe, deforming, and long-standing rheumatoid arthritis developed pure red cell aplasia that did not remit after withdrawal of medications, ran a chronic course, and in two patients remitted only after cytotoxic immunosuppressive treatment. An IgG inhibitor of autologous erythroid colony-forming and burst-forming unit growth in vitro was found in the serum of one patient. This specific erythropoietic inhibitor persisted in lower titer in the patient's serum even after an azathioprine-induced remission of pure red cell aplasia, indicating the possible need for maintenance immunosuppressive therapy. Chronic pure red cell aplasia may be another extra-articular manifestation of rheumatoid arthritis and should be considered when severe anemia develops in the absence of blood loss or hemolysis.