Pure red cell aplasia

INTRODUCTION: Pure red cell aplasia (PRCA) is an auto-immune mediated disorder with isolated hypoproliferation of the erythrocytes precursors in the bone marrow. It can be associated with thymoma. We present a case of this rare paraneoplastic syndrome and results of treatment.

CASE PRESENTATION: An otherwise healthy 71 year-old gentleman developed dyspnea and was found to have a severe anemia as low as 6.2 g/dL that required blood transfusion. His bone marrow examination showed marked erythroid hypoplasia, CD8-positive lymphocytosis, consistent with PRCA. Clonal T-cell receptor gene rearrangement and PCR for parvovirus B19 were negative. Tim patient was a previous smoker with a history of ehrlichiosis, tonsillectomy and vasectomy. Physical examination was unremarkable. The chest radiogram (Figure 1) showed an anterior mediastinal mass. The computerized chest CT (Figure 2)confirmed a 3 x 4 cm encapsulated mass. Pulmonary function tests were normal. Striated muscle antibody was positive. The patient underwent sternotomy and thyamomectomy. Pathology showed a mixed subtype thymoma invading into but not through the capsule. One month later, the patient remained anemic, requiring repeated blood transfusions. He was then given prednisone (1 mg/kg) for 8 weeks without improvement. He was subsequently treated with antithymocyte globulin therapy (ATG) and cyclosporine A. Two months later he was feeling better. His hemoglobin remained low but stable and he has not required any further transfusion since starling the cyclosporine A. Further follow up will be provided.

DISCUSSIONS: Acquired pure red cell aplasia is a rare condition of profound anemia with no reticulocytes and no erythroid precursors in the bone marrow. The association with thymoma is very rare. For example, in one study (1), from 1980 to 1994, 47 adult patients with PRCA were identified, of whom only 4 patients had thymoma. Up to forty percent of patients with thymoma present with one or more paraneoplastic syndromes, including myasthenia gravis, pure red cell aplasia, and hypogammaglobulinemia (2). In case of PRCA associated with thymoma, the mechanism involves suppression of erythropoiesis by nonclonal T cells. PRCA can occur before or after the discovery of thymoma. PRCA may disappear or persist after thymomectomy. In that latter case, prednisone alone or in combination with cytotoxic agents has a response rate of about 50%. Anti-thymocyte globulin therapy and tacrolimus seem promising. To date, the most effective agent, however, is cyclosporine A with a response rate of 82% in a series of 150 patients with PRCA (3). In the case reported, anemia was the revealing feature with a new onset dyspnea. A mediastinal mass was found on the chest radiogram. Although the surgery was a complete resection, PRCA persisted and did not improve with prednisone alone but appeared stabilized when associated with ATG and cyclosporine A. Due to the paucity of cases reported, no prospective study can be entertained to analyze accurately what the best therapeutic option would be. In our case, although a 6-month follow up seem encouraging, the long term prognosis remain uncertain since PRCA is a criterion of poor prognosis when associated with thymoma (4).

CONCLUSION: A case of PRCA associated with thymoma is reported. Although the surgical resection was complete, PRCA persisted and needed immunosuppressive therapy. The long term prognosis is uncertain.

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REFERENCES:

(1) Lacy MQ et al. Blood, 1996, 87: 3000-6.

(2) Morgenthaler TI et al, Mayo Clin Proc 1993, 68: 1110-23.

(3) Mamiya S et al, Eur J Haematol 1997, 59: 199-205.

(4) Nakayama H et al, Kyobu Geka. 1993, 46:13-20.

DISCLOSURE: Philippe Bauer, None.

Philippe R. Bauer MD * James R. Jett MD Mayo Clinic, Rochester, MN

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