{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T18:58:15Z","timestamp":1790621895265,"version":"4.1.0"},"reference-count":15,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T00:00:00Z","timestamp":1790553600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"},{"start":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T00:00:00Z","timestamp":1790553600000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["eJHaem"],"published-print":{"date-parts":[[2026,10]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:label\/>\n                    <jats:p>\n                      Pediatric essential thrombocythemia (ET) is extremely rare and frequently lacks identifiable driver mutations. We report a case of a 5\u2010year\u2010old male with ET harboring a novel\n                      <jats:italic>CALR<\/jats:italic>\n                      exon 9 frameshift mutation complicated by acquired von Willebrand syndrome. The patient presented with purpura, extreme thrombocytosis (1900\u00a0\u00d7\u00a010\n                      <jats:sup>9<\/jats:sup>\n                      \/L), and reduced von Willebrand factor activity. Antiplatelet therapy was avoided because of bleeding risk, and anagrelide was initiated. Treatment was associated with reduction in platelet count and improvement in von Willebrand factor activity. This case expands the molecular spectrum of pediatric\n                      <jats:italic>CALR<\/jats:italic>\n                      \u2010mutated ET and highlights the importance of individualized management in children with extreme thrombocytosis.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial Registration<\/jats:title>\n                    <jats:p>The authors have confirmed clinical trial registration is not needed for this submission.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/jha2.70399","type":"journal-article","created":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T17:55:07Z","timestamp":1790618107000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Pediatric Essential Thrombocythemia With a Novel\n                    <i>CALR<\/i>\n                    Mutation: A Case Report"],"prefix":"10.1002","volume":"7","author":[{"given":"Kana","family":"Tsuji","sequence":"first","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7461-9138","authenticated-orcid":false,"given":"Suguru","family":"Uemura","sequence":"additional","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tomoko","family":"Fujikawa","sequence":"additional","affiliation":[{"name":"Department of Pediatrics Graduate School of Medicine Kobe University  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nobuyuki","family":"Yamamoto","sequence":"additional","affiliation":[{"name":"Department of Pediatrics Graduate School of Medicine Kobe University  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aiko","family":"Kozaki","sequence":"additional","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Atsuro","family":"Saito","sequence":"additional","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Toshiaki","family":"Ishida","sequence":"additional","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takeshi","family":"Mori","sequence":"additional","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Makiko","family":"Yoshida","sequence":"additional","affiliation":[{"name":"Department of Pathology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takahiro","family":"Okutani","sequence":"additional","affiliation":[{"name":"Department of Pediatrics Saiseikai Hyogoken Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daiichiro","family":"Hasegawa","sequence":"additional","affiliation":[{"name":"Department of Hematology and Oncology Hyogo Prefectural Kobe Children's Hospital  Kobe Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2026,9,28]]},"reference":[{"issue":"20","key":"e_1_2_10_2_1","doi-asserted-by":"crossref","first-page":"2391","DOI":"10.1182\/blood-2016-03-643544","article-title":"The 2016 Revision to the World Health Organization Classification of Myeloid Neoplasms and Acute Leukemia","volume":"127","author":"Arber D. A.","year":"2016","journal-title":"Blood"},{"issue":"25","key":"e_1_2_10_3_1","doi-asserted-by":"crossref","first-page":"2379","DOI":"10.1056\/NEJMoa1311347","article-title":"Somatic Mutations of Calreticulin in Myeloproliferative Neoplasms","volume":"369","author":"Klampfl T.","year":"2013","journal-title":"New England Journal of Medicine"},{"issue":"2","key":"e_1_2_10_4_1","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1038\/leu.2015.277","article-title":"Differential Clinical Effects of Different Mutation Subtypes in CALR\u2010Mutant Myeloproliferative Neoplasms","volume":"30","author":"Pietra D.","year":"2016","journal-title":"Leukemia"},{"issue":"11","key":"e_1_2_10_5_1","doi-asserted-by":"crossref","DOI":"10.1038\/bcj.2015.94","article-title":"Practice\u2010Relevant Revision of IPSET\u2010Thrombosis Based on 1019 Patients With WHO\u2010Defined Essential Thrombocythemia","volume":"5","author":"Barbui T.","year":"2015","journal-title":"Blood Cancer Journal"},{"issue":"6","key":"e_1_2_10_6_1","first-page":"507","article-title":"Thrombocytosis in Children","volume":"63","author":"Chiarello P.","year":"2011","journal-title":"Minerva Pediatrica"},{"issue":"8","key":"e_1_2_10_7_1","doi-asserted-by":"crossref","first-page":"1580","DOI":"10.3324\/haematol.2018.200832","article-title":"Characteristics and Outcomes of Patients With Essential Thrombocythemia or Polycythemia Vera Diagnosed Before 20 Years of Age: A Systematic Review","volume":"104","author":"Ianotto J.\u2010C.","year":"2019","journal-title":"Haematologica"},{"issue":"2","key":"e_1_2_10_8_1","doi-asserted-by":"crossref","first-page":"266","DOI":"10.1007\/s12185-016-2022-2","article-title":"JAK2, MPL, and CALR Mutations in Children With Essential Thrombocythemia","volume":"104","author":"Sekiya Y.","year":"2016","journal-title":"International Journal of Hematology"},{"issue":"1","key":"e_1_2_10_9_1","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1002\/jha2.39","article-title":"Clinical Features of Children With Polycythemia Vera, Essential Thrombocythemia, and Primary Myelofibrosis in Japan: A Retrospective Nationwide Survey","volume":"1","author":"Ishida H.","year":"2020","journal-title":"EJHaem"},{"issue":"3","key":"e_1_2_10_10_1","doi-asserted-by":"crossref","first-page":"520","DOI":"10.1111\/bjh.18646","article-title":"Clinical and Molecular Characteristics of Forty Chinese Children With Essential Thrombocythemia: A Single\u2010Center, Retrospective Analysis","volume":"201","author":"Zhang L.","year":"2023","journal-title":"British Journal of Haematology"},{"issue":"4","key":"e_1_2_10_11_1","doi-asserted-by":"crossref","first-page":"620","DOI":"10.3324\/haematol.2013.092684","article-title":"Primary Thrombocytosis in Children","volume":"99","author":"Kucine N.","year":"2014","journal-title":"Haematologica"},{"key":"e_1_2_10_12_1","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.ejim.2016.11.011","article-title":"Factors Related to the Development of Acquired von Willebrand Syndrome in Patients With Essential Thrombocythemia and Polycythemia Vera","volume":"41","author":"Rottenstreich A.","year":"2017","journal-title":"European Journal of Internal Medicine"},{"issue":"8","key":"e_1_2_10_13_1","doi-asserted-by":"crossref","first-page":"926","DOI":"10.3324\/haematol.2016.146654","article-title":"Antiplatelet Therapy Versus Observation in Low\u2010Risk Essential Thrombocythemia With a CALR Mutation","volume":"101","author":"Alvarez\u2010Larran A.","year":"2016","journal-title":"Haematologica"},{"issue":"4","key":"e_1_2_10_14_1","doi-asserted-by":"crossref","first-page":"358","DOI":"10.1111\/j.1600-0609.2006.00719.x","article-title":"Long\u2010Term Use of Anagrelide in the Treatment of Children With Essential Thrombocythemia","volume":"77","author":"Lackner H.","year":"2006","journal-title":"European Journal of Haematology"},{"issue":"9","key":"e_1_2_10_15_1","doi-asserted-by":"crossref","first-page":"1017","DOI":"10.1111\/ped.13330","article-title":"Efficacy and Safety of Anagrelide in Childhood Essential Thrombocythemia","volume":"59","author":"Kanai A.","year":"2017","journal-title":"Pediatrics International"},{"key":"e_1_2_10_16_1","doi-asserted-by":"crossref","DOI":"10.1016\/j.leukres.2022.106962","article-title":"Anagrelide in Essential Thrombocythemia: Efficacy and Long\u2010Term Consequences in Young Patient Population","volume":"123","author":"Bieniaszewska M.","year":"2022","journal-title":"Leukemia Research"}],"container-title":["eJHaem"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/jha2.70399","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/full-xml\/10.1002\/jha2.70399","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/jha2.70399","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T17:55:10Z","timestamp":1790618110000},"score":1,"resource":{"primary":{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/jha2.70399"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,28]]},"references-count":15,"journal-issue":{"issue":"5","published-print":{"date-parts":[[2026,10]]}},"alternative-id":["10.1002\/jha2.70399"],"URL":"https:\/\/doi.org\/10.1002\/jha2.70399","archive":["Portico"],"relation":{},"ISSN":["2688-6146","2688-6146"],"issn-type":[{"value":"2688-6146","type":"print"},{"value":"2688-6146","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,28]]},"assertion":[{"value":"2026-08-13","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-09-16","order":2,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-09-28","order":3,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e70399"}}