Fifty cases of chronic pure red cell aplasia in adults (idiopathic in 32 cases, associated with chronic lymphocytic leukaemia in 18) were followed up after studying their erythroblastic precursors in vitro. Analysis of response to immunomodulators confirmed the existence, in patients with idiopathic chronic pure red cell aplasia, of a relationship between in vitro behaviour and obtention of a remission: patients with normal differentiation of erythroblasts consistently responded to treatments, whereas treatments were usually ineffective when the erythroblasts did not differentiate in vitro. When in vitro differentiation was below normal, responses to treatments were varied. In patients with chronic lymphocytic leukaemia, the erythroblastic precursors were normal in 15/18 cases, and response to immunomodulators was observed in 13/18 cases. A second objective of this study was to determine, on a large series, the most adequate immunomodulator treatment. In idiopathic chronic pure red cell aplasia the most efficient therapy was corticosteroids and cyclophosphamide administered separately or together. The antilymphocyte serum gave disappointing results. In pure red cell aplasia associated with leukaemia cyclophosphamide was the most frequently effective drug, with corticosteroids taking second rank; however, infections were frequent. The treatments to be considered when both corticosteroids and cyclophosphamide fail are discussed.
