1 Department of Medicine and 2 Division of Nephrology, University of British Columbia, St Paul's Hospital and 3 Kidney Function Clinic, Vancouver BC, Canada
Correspondence and offprint requests to: A. Levin, MD FRCPC, University of British Columbia, Division of Nephrology, St Paul's Hospital, 1081 Burrard Street Rm 6010A, Vancouver BC, Canada V6Z 1Y8. Email: alevin{at}providencehealth.bc.ca
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Abstract |
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Keywords: darbepoetin; erythropoietin; pure red cell aplasia; steroids
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Introduction |
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Case |
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Bone marrow biopsy done on August 29, 2003 revealed normal myeloid and megakaryocyte lines with absent red cell lines, consistent with the diagnosis of PRCA. Investigations in hospital, including an autoimmune screen, infectious serology and total body computed tomography, did not reveal any secondary cause of her PRCA. A serum sample was sent to PPD Development, CLIA Immunochemistry Laboratory in Richmond, Virginia for evaluation of serum erythropoietin levels and the presence of anti-erythropoeitin antibodies. Tests performed on September 9, 2003 revealed an inappropriately normal serum erythropoietin level of 23.7 mU/ml (normal range 1030 mU/ml) and positive serum erythropoietin antibody levels by anti-erythropoeitin radioimmunoprecipitation at 1.7% c.p.m. at 1:100 dilution (positive 0.9% c.p.m. at 1:20 dilution) [8].
On September 25, 2003, 16 months after starting epoetin therapy, Eprex was discontinued and immunosuppressive therapy was initiated with prednisone 60 mg daily and cyclophosphamide 100 mg per os daily; the latter was discontinued after 5 days secondary to intolerance. At initiation of immunosuppressive therapy, her haemoglobin remained low at 73 g/l with persistent absence of reticulocytes (0x109/l). She remained transfusion dependent between September 25 and October 28, 2003, requiring 3 units every 2 weeks (total 15 units transfused), see Figure 1.
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At the time of her last transfusion, January 27, 2004, her reticulocytes were 52x109/l on 20 mg per day of prednisone, with a corresponding haemoglobin of 78 g/l. By February 25, 2004, on 10 mg of prednisone, she had maintained a haemoglobin of 103 g/l. Her creatinine remained steady at 246 µmol/l (eGFR 17 ml/min/1.73 m2) without dialysis. Tests performed at the CLIA Laboratory on March 2, 2004 revealed negative serum erythropoietin antibody levels at 0.2% c.p.m. at 1:20 dilution (negative 0.6% c.p.m. at 1:20 dilution) [8].
Given the negative antibody status and the continued slow decline in haemoglobin, the decision was made to reinitiate erythropoietin therapy with Aranesp 20 µg s.c. every 14 days (darbepoetin-; Amgen) under the cover of 7.5 mg per day of prednisone on March 19, 2003. Tests performed on June 24 revealed persistently negative serum erythropoietin antibody levels at 0.3% c.p.m. at 1:20 dilution (negative
0.6% c.p.m.) while on Aranesp 20 µg s.c. every 7 days and prednisone 5 mg per day. At this time, her haemoglobin peaked at 110 g/l (reticulocyte count of 27x109/l) and was maintained at 110 g/l (reticulocyte count of 15x109/l) 1 month later. On July 20, 2004, due to intolerable side effects and at the patient's insistence, prednisone therapy was halted.
Blood work-up over the next 2 months revealed a continued decline in her haemoglobin to 74 g/l and a persistent reticulocytopenia at 5x109/l. Given the possibility of PRCA, Aranesp therapy was discontinued and prednisone reinitiated at 50 mg per day. Blood transfusions were reinitiated at a rate of 2 units every 2 weeks. On November 12, 2004, anti-erythropoietin antibodies were again found to be positive at 1.2% c.p.m. at 1:100 dilution (positive 0.9% c.p.m. at 1:20 dilution) [8], see Figure 1.
While on 50 mg of prednisone per day, her transfusion requirements decreased, requiring 3 units of packed red cells on November 12, 2004 and December 1, 2004. Subsequent blood work-up revealed a rising reticulocyte count with concurrent reduction of her prednisone dose, reaching a peak of 90x109/l on January 10, 2005 while on 35 mg of prednisone daily. Testing done on January 19, 2005 revealed negative anti-erythropoietin antibodies (0.1% c.p.m. at 1:20 dilution; negative 0.6% c.p.m. at 1:20 dilution) [8].
At the time of writing, she is not taking any erythropoiesis-stimulating agent. Given her intolerance to prednisone, imuran 50 mg per day (azathioprine) was introduced for its steroid-sparing effect. Unfortunately, medication intolerance has forced her physicians to reduce the dosage of both prednisone (10 mg per day) and imuran (25 mg every other day). Transfusions are now required at a rate of 3 units every 4 weeks, although the interval is increasing. Reticulocyte count is currently 34x109/l with a haemoglobin of 103 g/l. The patient remains depressed but is otherwise clinically stable.
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Discussion |
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PRCA is a rare syndrome of anaemia associated with low reticulocyte count, absent bone marrow erythroblasts, resistance to epoetin therapy and anti-erythropoietin antibodies [2,4,7]. It has been attributed to the induction of an IgG antibody directed against the protein moiety of the glycosylated erythropoietin polypeptide [1,4,9,10]. Typically, PRCA occurs after 367 months of therapy with recombinant epoetin [1,7], with a median occurrence after 9 months of therapy for Eprex [2,6]. As a phenomenon, PRCA markedly increased after 1998, peaked in 2001 and then slowly declined thereafter [25,7,9,11]. Although rarely described before 1996 (four cases),
200 cases were described between January 1998 and March 2003 [4].
The dramatic rise in incidence after 1998 has been attributed to various changes in the Eprex formulation, handling and delivery that are thought to have conferred an increase in immunogenicity [2,7,9]. The changes included the substitution of polysorbate 80 and glycine for human serum albumin as stabilizer, the use of exposed rubber plungers and silicone oil lubricant in pre-filled syringes, the shift from the intravenous (i.v.) to the s.c. route of administration, and self-administration which is associated with problems in storage (i.e. >8°C) and handling [1,6,7,9].
Our patient developed PRCA in the context of all these changes, having started therapy with pre-filled syringes of Eprex administered by the s.c. route in May of 2002. Although diagnosis was confirmed in September 2003, it is likely that she started to manifest the effects of PRCA as early as December 2002, 7 months after the initiation of Eprex therapy, as indicated by the need for increasing doses without effect. Her clinical course post-development of PRCA was typical of previously described cases. After her haemoglobin peaked in December 2002January 2003, she demonstrated a progressive decline in haemoglobin values over the subsequent 8 months, eventually becoming transfusion dependent.
To our knowledge, this is the first reported case of PRCA relapse in a patient with negative anti-erythropoietin antibodies documented during rechallenge with a different erythropoiesis-stimulating agent.
While previous reviews have suggested variable effectiveness of immunosuppressant therapy, our patient demonstrated complete resolution of previously demonstrated anti-erythropoietin antibodies with prednisone therapy alone [1,2,6,7,11]. Her transfusion requirements decreased from 1 unit per week to 1 unit every 2 weeks after only 6 weeks of therapy. After only 19 weeks of progressively weaning her off prednisone therapy, she received her last unit of transfusion, maintained a haemoglobin in the high 80s to low 90s g/l, and demonstrated a negative serum erythropoietin antibody.
Subsequently, while on low dose therapy, antibody-negative status was maintained by the chronic immunosuppression. This allowed us successfully to reintroduce erythropoiesis-stimulating agent therapy with therapeutic effect. As demonstrated by our patient, darbapoietin therapy with concomitant low dose prednisone successfully increased our patient's haemoglobin from 90 to 110 g/l. Unfortunately, cessation of prednisone therapy resulted in a recurrence of PRCA, which to our knowledge is one of the first reported cases of PRCA relapse in a patient with negative anti-erythropoietin antibodies documented during rechallenge with a different erythropoiesis-stimulating agent.
Mandreoli et al., in their report demonstrating the effectiveness of rituximab at terminating PRCA and allowing for successful reintroduction of therapy [12], postulated that the beneficial effect of rituximab was maintained at 1 year via suppression of B-cell regeneration and, by extension, antibody production. It is possible that the high dose prednisone therapy was able to terminate anti-erythropoietin antibody production and/or secretion in our patient through non-specific mechanisms. The subsequent low dose prednisone maintained this B-cell suppression and allowed successful reintroduction of therapy with a different erythropoiesis-stimulating agent by inhibiting new antibody production and/or secretion. Under this cover of low dose prednisone, our patient was able to increase her haemoglobin successfully, demonstrating that the therapy was in fact successful for a period of time. It is postulated that only when we ceased the chronic immunosuppression therapy were the primed memory cells able to re-secrete antibodies, causing a delayed recurrence of her previous PRCA. This assertion of the immunoprotective effects of prednisone is substantiated by both the absence of anti-erythropoietin antibodies on testing 3 months post re-introduction of darbapoietin and the almost immediate recurrence of PRCA post-prednisone discontinuation.
The importance of this clinical course is implied from the previous case reports and reviews present in the literature. Previous reviews and case reports have offered renal transplant as a potential alternative to exogenous erythropoiesis-stimulating agent therapy, and the debate as to whether renal transplantation itself or the use of immunosuppressive agents accounts for the success of this therapy continues [2,6,11,13]. For those who are not transplant candidates, treatment of the persistent anaemia has been limited to transfusions, given the recommendation to avoid any re-introduction of erythropoietin therapy [1,7]. This case demonstrates that erythropoiesis-stimulating agent therapy may be successfully re-instituted if combined with chronic low dose prednisone therapy. It also demonstrates that cessation of the immunotherapy may result in recurrence. Unfortunately, due to patient intolerance, we were not able to test our hypothesis that steroid-sparing agents, such as azathioprine, would have similar effects to prednisone. More work is needed to understand the mechanism of PRCA in individuals with CKD.
Conflict of interest statement. Dr Levin is a member of the speaker's bureau and advisory board, she also conducts reasearch with Janssen-Cilag, OrthoBiotech, Roche and Amgen. All other authors declare no conflict of interest.
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