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CASE REPORT Hydroxyurea-induced cyclic in

Abstract Hydroxyurea is an orally administered medication that is frequently used in the treatment of myeloproliferative disorders as well as sickle cell disease. Cyclical thrombocytopenia during hydroxyurea therapy is an unusual and largely under-recognized side effect. We herein describe a case of a 66-year-old man with polycythemia vera who was started on hydroxyurea, and who subsequently developed count oscillations with peak platelet levels as high as 2900 × 109/L, and nadirs as low as 8 × 109/L. We also performed a literature review of the currently published cases of hydroxyurea-induced cyclic thrombocytopenia. Keywords: , thrombocytopenia, hydroxyurea, platelet count oscillation, polycythemia vera

Introduction treated with phlebotomies and 162 Karlton Wong* and mg daily. Hydroxyurea was introduced 1 year Hydroxyurea is an orally administered Michael H Rosove after diagnosis, 1.5 gm daily, not adjusted for medication useful in myeloproliferative University of California, Los Angeles, platelet count. Department of Medicine, Division of disorders and sickle cell disease [1,2]. The Oncology, US drug blocks ribonucleotide reductase, About a year after hydroxyurea was *Author for correspondence: inhibiting DNA synthesis and repair. It started, he had a petechial rash on the legs 9 [email protected]; causes myelosuppression and macrocytosis, and platelet count 15 × 10 /L. Prednisone was [email protected] and it increases fetal hemoglobin levels given, and the platelet count improved within [3,4]. Unwanted side effects includedays. He was therefore considered to have gastroenterological symptoms, eczema, idiopathic thrombocytopenic (ITP). and distal leg skin ulceration [4]. Cyclic Thrombocytopenia recurred periodically; the thrombocytopenia is rare, and thus practicing lowest platelet count recorded was 8 × 109/L, hematologists may be unaware of the and the highest was 2900 × 109/L. The WBC phenomenon [5-9]. We herein describe a remained stable throughout. Rituximab, case that is a helpful reminder of this unusual azathioprine, mycophenolate, and cyclosporin but important problem, where platelet were each briefly tried and were ineffective in levels oscillate from thrombocytosis to preventing platelet count nadirs. The patient thrombocytopenic ranges. experienced neither thromboembolism nor (apart from petechiae at platelet Case Report count nadirs). The patient is a 66-year-old male with In retrospect, predictable cycling was noted a 9-year history of polycythemia vera with a period of about 28 days, unaffected associated with a jak2 exon 12 mutation by “ITP” treatment. Hydroxyurea was (N542-E543 deletion). He presented with discontinued. The platelet count peaked 12 9 RBC 7.44 × 10 /L, hemoglobin 18.6 gm/ days later at 2907 × 109/L with undetectable dL, hematocrit 61.7%, MCV 83 fL, platelet serum (normal range 7-99 9 9 count 405 × 10 /L, and WBC 6.3 × 10 /L. pg/mL). was introduced and Serum erythropoietin level was 2.5 mU/mL escalated to 20 mg twice daily. In the ensuing (normal range, 5.0-24.6 mU/mL). He was 110 days after the peak platelet count, platelet

1281 Clin. Pract. (2019) 16(5), 1281-1283 ISSN 2044-9038 CASE REPORT Wong & Rosove

counts ranged from 659-1211 × 109/L with 188 consecutive patients with Philadelphia no regular cycling. Serum thrombopoietin chromosome-negative myeloproliferative ranged from 49-116 pg/mL. neoplasms [9]. Hydroxyurea was used in 149 patients. Platelet count cycling was defined Discussion and Conclusion as a spread between peak and nadir counts Tefferi et al. described 2 polycythemia greater than 100 × 109/L. Twenty-nine of the vera patients treated with hydroxyurea who 188 patients (15.4%) demonstrated cycling, had platelet count oscillations from 35-1412 25 of whom had received hydroxyurea; 4 had × 109/L and periods from 27 to 66 days [5]. . Most oscillations were modest, Serum thrombopoietin levels fluctuated out amplitudes ranging from 100-500 × 109/L of phase with platelet counts. Both patients in 23 of 29 patients. Only in 6 were they improved with hydroxyurea discontinuation. greater than 500 × 109/L; 2 were greater than One had recurrent cycling when rechallenged 1200 × 109/L. The 4 patients with cycling on with the drug. anagrelide had amplitudes less than 100 × 109/L. Treatment was changed in 7 patients 4 cases were reported by Steensma et al. and not changed in 22. No patient had [6] Platelet counts ranged from 34-1479 or bleeding. × 109/L, and cycles lasted 20 to 30 days. One patient had vasomotor symptoms with Based on reports in the medical literature elevated platelet counts; another developed coupled with the patient in this report, mild digital ischemia. In 3 cases, lower peaks and to moderate platelet count oscillations during higher nadirs could be achieved by not altering hydroxyurea therapy for myeloproliferative hydroxyurea dosage during oscillations. disorders appear not to be rare, but most cases probably escape notice. Patients with Burthem et al. [7] reported a patient with large oscillations appear to be rare but jak2 V617F mutated polycythemia vera in understandably more readily recognized. 2008 with platelet count cycling beginning Patients may be mistakenly diagnosed with 3 months after hydroxyurea was started. The ITP as the initiation of ITP therapy is likely platelet count range was 200-800 × 109/L with to be followed by “response” when it is only a 28-day cycle. Peaks and troughs became less a spontaneous upswing of the oscillatory marked when hydroxyurea dosage was not cycle. The commonest cycling period seems adjusted for the platelet count. to be about 25 to 30 days, which can make Tauscher et al. [8] reported 12 jak2 V617F it difficult to identify affected patients, mutated polycythemia vera patients who especially when peaks and troughs are subtle had large platelet count fluctuations during unless frequent testing is done. Despite hydroxyurea treatment. One patient’s platelet extreme platelet count fluctuations in some count range was 27-4900 × 109/L; 6 patients patients, serious complications appear to had nadirs less than 100 × 109/L, 3 of whom be unusual. Withdrawal of hydroxyurea had nadirs less than 50 × 109/L. Nine patients ameliorates extreme cycling. How often stable had peaked over 1000 × 109/L. Cycling periods hydroxyurea dosing might be continued ranged from 27 to 30 days. Five patients also safely requires further clarification. Thus far, had WBC fluctuations with a 26-29 day the mechanism for cyclic thrombocytopenia cycle, counts ranging from 1.9-38.2 × 109/L. remains unclear; however, based on Tefferi’s Most oscillations stopped with hydroxyurea observation that the thrombopoietin level discontinuation; in 2 patients, oscillations may fluctuate out of phase with the platelet gradually disappeared while hydroxyurea was count, [5] as we also observed, hydroxyurea continued. No thromboembolic or bleeding may alter the stability of the thrombopoietin events were reported. feedback loop, destabilizing the signaling mechanism of the megakaryocyte progenitor The last report we are aware of was pool [5,10]. published in 2014, a retrospective analysis of

1282 10.4172/clinical-practice.1000476 Clin. Pract. (2019) 16(5) CASE REPORT Wong & Rosove

References Tefferi A, Elliott MA, Kao PC, et al. Tauscher J, Siegel F, Petrides PE. Hydroxyurea-induced marked oscillations Hydroxyurea-induced oscillations in Agrawal RK, Patel RK, Shah V, et al. of platelet counts in patients with twelve patients with polycythemia vera. Hydroxyurea in sickle cell disease: drug polycythemia vera. Blood. 96(4), 1582- Haematological. 95(7), 1227-1229 (2010). review. Indian J. Hematol. Blood Transfus. 1584 (2000). 30(2), 91-96 (2014). Verner E, Forsyth C, Grigg A. Cyclical Steensma DP, Harrison CN, Tefferi thrombocytosis, acquired von Willebrand Tefferi A, Barbui T. Polycythemia vera A. Hydroxyurea-associated platelet count syndrome and aggressive non-melanoma and essential : 2017 oscillations in polycythemia vera: A report skin cancers are common in patients with update on diagnosis, risk-stratification, of four new cases and a review. Leukemia. Philadelphia-negative myeloproliferative and management. Am. J. Hematol. 92(1), 42(6), 1243-1253 (2001). neoplasms treated with hydroxyurea. Leuk. 94-108 (2017). Lymphoma. 55(5), 1139-1143 (2014). Burthem J, Chaudhry MS. Yarbro JW. Mechanism of action of associated platelet Santillan M, Mahaffy JM, Belair hydroxyurea. Semin. Oncol. 1-10 (1992). count oscillations in a patient with J, Mackey MC. Regulation of platelet Randi ML, Ruzzon E, Tezza F, et al. polycythemia vera. A case report and production: the normal response to Toxicity and side effects of hydroxyurea review of the literature. Platelets. 19(3), perturbation and cyclical platelet disease. used for primary thrombocytopenia. 234-235 (2008). J. Theor. Biol. 206, 585-603 (2000). Platelets. 16(3/4), 181-184 (2005).

1283 10.4172/clinical-practice.1000476 Clin. Pract. (2019) 16(5)