THE PATHOPHYSIOLOGY OF PURE RED-CELL APLASIA - IMPLICATIONS FOR THERAPY

To determine the utility of marrow culture in defining the natural his tory and therapeutic response of pure red cell aplasia we have studied 37 patients. Patients were evaluated at the University of Washington before specific therapies (n = 21) or at the time of treatment failure (n = 16). Evaluation included a medical and drug exposure history, a physical examination, a chest x-ray or computed tomography to rule out thymoma, lymphocyte immunophenotype studies, anti-nuclear antibody an d rheumatoid factor determinations, marrow cytogenetics, and marrow pr ogenitor cell cultures. Retrospective Southern analyses to detect huma n parvovirus B19 was performed in the 27 patients for whom sera was st ored. Clinical follow-up was obtained to document therapeutic response s. Normal burst forming unit-erythroid (BFU-E) growth (>30 bursts/10(5 ) marrow mononuclear cells [MMNC]) in culture proved an outstanding pr edictor of clinical response, as 27 of 29 individuals with normal freq uencies of erythroid bursts in culture responded to immunomodulating t herapies (sensitivity 96%, specificity 78%, predictive value 93%, P = .0001 with two-tailed chi square analysis). Overall, 28 patients respo nded to either immunomodulating therapies or drug withdrawal. Twenty-f our patients obtained a normal hematocrit (complete response [CR]) and 4 additional patients became transfusion independent (partial respons e). Although responding patients often required several therapies, 20 of 24 (83%) patients who obtained a CR have sustained a normal hematoc rit without maintenance therapy at the time of last follow-up (median 5 years). In contrast, of 8 patients with poor in vitro BFU-E growth ( <6 bursts/10(5) MMNC), 7 failed to respond to any therapy and all died (median survival time 17 months). Our data suggest that in individual s, from whom BFU-E mature appropriately in culture, immunosuppressive drugs should be used sequentially until a CR is obtained and a durable remission is the expected outcome. (C) 1996 by The American Society o f Hematology.