Essential thrombocythaemia in children
Authors:
D. Pospíšilová 1; J. Veselovská 2; M. Horváthová 2; R. Solná 2; J. Kučerová 2; J. Čmejlová 3; R. Čmejla 3; M. Beličková 3; S. Peková 4; K. Petrtýlová 5; V. Mihál 1; T. Votava 6; J. Hak 7; O. Zapletal 8; J. Starý 5; V. Divoký 2
Authors‘ workplace:
Dětská klinika LF UP a FN v Olomouci, 2Ústav biologie LF UP v Olomouci, 3Ústav hematologie a krevní transfúze
Oddělení buněčné fyziologie, Praha, 4Oddělení klinické biochemie, hematologie a imunologie, Nemocnice na Homolce
Praha 5Klinika dětské hematologi
; Dětská klinika LF UK a FN Hradec Králové, 8Oddělení klinické hematologie FN Brno
7
Published in:
Transfuze Hematol. dnes,14, 2008, No. 2, p. 63-70.
Category:
Comprehensive Reports, Original Papers, Case Reports
Overview
Essential thrombocythaemia (ET), a Philadelphia chromosome negative chronic myeloproliferative disorder, is usually a disease of middle age and it is extremely rare in paediatric population. In this report we have analysed 15 children (9 girls and 6 boys) diagnosed with ET in the Czech paediatric population from 1987 to 2007. There is a growing incidence of ET in children: 0.1/1 million children/year in years 1987–1996 but 0.6/1 million children/year in years 1997–2006. Platelet count at the time of diagnosis was 681–2428x10⁹/l (median 1720x10⁹/l), Hb and leukocyte counts were within normal range. Splenomegaly was found in 8 children. The median follow-up was 19 months. The clinical picture in our paediatric patients was milder than in adults. The diagnosis was made only during routine blood analysis in more than half of the cases. No thrombosis or major bleeding was observed at the time of diagnosis, although symptoms of microvascular obstruction were present in some patients. Erythropoietin (Epo) hypersensitivity of haematopoietic progenitors in vitro was found in the majority of the patients (11/13), with EEC formation in 9/11 patients. These results are indicative of the diagnosis of myeloproliferative disease. We detected JAK2 V617F mutation in peripheral blood leukocytes or in separated platelets only in one female patient with borderline level of haemoglobin. Monoclonal haematopoiesis was noted only in one another female patient. During the EEC analysis we found some colonies bearing heterozygous or homozygous V617F mutation in 3/5 examined patients. Our data suggests that childhood ET patients could bear minor JAK2 V617F-positive subclones. These patients did not show any phenotypic differences from the cohort. Treatment strategies for paediatric ET have not yet been fully defined. The treatment approach to our paediatric patients was variable. As the majority of paediatric haematologists prefer anagrelide to hydroxyurea, 6 patients were treated with anagrelide, 5 patients with acetylosalicylic acid and in 4 patients the „wait and see“ strategy was used. United approach towards the diagnosis and treatment of childhood ET is still to be established. The paediatric patients have to be closely monitored in case of possible disease progression to clonal haematopoiesis, of appearance of JAK2 V617F mutation, or of evolvement into clinical picture of polycythaemia vera. Finally, the question if adult and paediatric ET are different stages of the same disease or whether they represent separate disorders is still to be answered possibly by international cooperation in large multicentral studies and by long-term monitoring of paediatric patients.
Key words:
essential thrombocythaemia, children, clonality, erythroid colonies, hypersensitivity to erythropoietin, JAK2 V617F mutation
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