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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" article-type="research-article" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Pediatric Hematology/Oncology and Immunopathology</journal-id><journal-title-group><journal-title xml:lang="en">Pediatric Hematology/Oncology and Immunopathology</journal-title><trans-title-group xml:lang="ru"><trans-title>Вопросы гематологии/онкологии и иммунопатологии в педиатрии</trans-title></trans-title-group></journal-title-group><issn publication-format="print">1726-1708</issn><issn publication-format="electronic">2414-9314</issn><publisher><publisher-name xml:lang="en">Fund Doctors, Innovations, Science for Children</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">1072</article-id><article-id pub-id-type="doi">10.24287/j.1072</article-id><article-categories><subj-group subj-group-type="toc-heading" xml:lang="en"><subject>CLINICAL OBSERVATIONS</subject></subj-group><subj-group subj-group-type="toc-heading" xml:lang="ru"><subject>КЛИНИЧЕСКИЕ НАБЛЮДЕНИЯ</subject></subj-group><subj-group subj-group-type="article-type"><subject>Research Article</subject></subj-group></article-categories><title-group><article-title xml:lang="en">Transient abnormal myelopoiesis in children with Down syndrome: a literature review and clinical case presentation</article-title><trans-title-group xml:lang="ru"><trans-title>Транзиторный аномальный миелопоэз у детей с синдромом Дауна: обзор литературы и презентация клинических случаев</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-2731-4531</contrib-id><name-alternatives><name xml:lang="en"><surname>Boychenko</surname><given-names>E. G.</given-names></name><name xml:lang="ru"><surname>Бойченко</surname><given-names>Э. Г.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Dr. Med. Sci., Head of Oncology Department No. 6 – for the Treatment of Children with Leukemia Using Intensive Chemotherapy Regimens</p></bio><bio xml:lang="ru"><p>д-р мед. наук, заведующая онкологическим отделением №6 – для лечения детей, страдающих лейкемией, с применением интенсивной химиотерапии</p></bio><email>boychenko-elmira@yandex.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-6054-200X</contrib-id><name-alternatives><name xml:lang="en"><surname>Lebedenko</surname><given-names>E. A.</given-names></name><name xml:lang="ru"><surname>Лебеденко</surname><given-names>Е. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>boychenko-elmira@yandex.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0009-1408-8270</contrib-id><name-alternatives><name xml:lang="en"><surname>Garbuzova</surname><given-names>I. A.</given-names></name><name xml:lang="ru"><surname>Гарбузова</surname><given-names>И. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><email>boychenko-elmira@yandex.ru</email><xref ref-type="aff" rid="aff1"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">Children's Multi-Specialty Clinical Center of High Medical Technologies</institution></aff><aff><institution xml:lang="ru">СПб ГБУЗ «Детский городской многопрофильный клинический специализированный центр высоких медицинских технологий»</institution></aff></aff-alternatives><pub-date date-type="pub" iso-8601-date="2026-04-14" publication-format="electronic"><day>14</day><month>04</month><year>2026</year></pub-date><volume>25</volume><issue>1</issue><issue-title xml:lang="en"/><issue-title xml:lang="ru"/><fpage>166</fpage><lpage>174</lpage><history><date date-type="received" iso-8601-date="2026-01-26"><day>26</day><month>01</month><year>2026</year></date><date date-type="accepted" iso-8601-date="2026-02-11"><day>11</day><month>02</month><year>2026</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2026, «D. Rogachev NMRCPHOI»</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2026, ФГБУ «НМИЦ ДГОИ им. Дмитрия Рогачева» Минздрава России</copyright-statement><copyright-year>2026</copyright-year><copyright-holder xml:lang="en">«D. Rogachev NMRCPHOI»</copyright-holder><copyright-holder xml:lang="ru">ФГБУ «НМИЦ ДГОИ им. Дмитрия Рогачева» Минздрава России</copyright-holder><ali:free_to_read xmlns:ali="http://www.niso.org/schemas/ali/1.0/"/><license><ali:license_ref xmlns:ali="http://www.niso.org/schemas/ali/1.0/">https://creativecommons.org/licenses/by/4.0</ali:license_ref></license></permissions><self-uri xlink:href="https://hemoncim.com/jour/article/view/1072">https://hemoncim.com/jour/article/view/1072</self-uri><abstract xml:lang="en"><p>Down syndrome is a condition characterized by an extra copy of chromosome 21 resulting, among other things, in an increased susceptibility to blood disorders. Transient abnormal myelopoiesis is a unique phenomenon observed in neonates with Down syndrome. Typically, it presents in the neonatal period as a transient clonal expansion of blasts, often remaining clinically insignificant and undergoing spontaneous regression within the first 5 weeks of life. However, despite its transient nature, this condition should still be carefully monitored due to the high risk of its transformation into myeloid leukemia of Down syndrome which occurs in 20–30% of cases within the first 5 years of life. Acute myeloid leukemia and myeloid leukemia associated with Down syndrome arise from the same underlying genetic predisposition and are characterized by the proliferation of megakaryoblasts harboring a mutation in the <italic>GATA1</italic> gene. Comprehensive assessment including morphology, immunophenotyping and cytogenetic and molecular genetic testing helps in differential diagnosis and facilitates therapeutic decision-making. Here, we present a literature review and report 2 clinical cases of transient abnormal myelopoiesis demonstrating the nature of this condition as well as its typical diagnostic features that enable prompt differential diagnosis and hence, timely initiation of supportive and cytoreductive therapy, while also highlighting the importance of careful monitoring in patients with Down syndrome.</p></abstract><trans-abstract xml:lang="ru"><p>Синдром Дауна характеризуется наличием экстракопии хромосомы 21, что обусловливает повышенную подверженность гематологическим заболеваниям. Транзиторный аномальный миелопоэз является уникальным феноменом, который наблюдается у новорожденных с синдромом Дауна. В типичных случаях он презентирует в периоде новорожденности в виде транзиторной клональной экспансии бластов, нередко остается клинически незначимым и спонтанно регрессирует в течение первых 5 недель жизни. Тем не менее, несмотря на транзиторный характер, это состояние требует тщательного мониторирования вследствие высокого риска трансформации в миелоидную лейкемию, ассоциированную с синдромом Дауна, которая имеет место в 20–30% случаев в течение первых 5 лет жизни. Острый миелоидный лейкоз и миелоидная лейкемия, ассоциированная с синдромом Дауна, возникают на одинаковой основе генетической предрасположенности, характеризуются пролиферацией мегакариобластов, несущих мутацию в гене <italic>GATA1</italic>. Комплексное обследование, включающее морфологию, иммунофенотипирование, цитогенетическое и молекулярно-генетическое исследования, помогает в проведении дифференциального диагноза и способствует принятию терапевтических решений. Мы представляем обзор литературы и 2 клинических случая транзиторного аномального миелопоэза, демонстрирующих природу этого состояния, типичные диагностические признаки, позволяющие ускорить проведение дифференциального диагноза в целях своевременного назначения сопроводительной и циторедуктивной терапии, а также подтверждающих значение тщательного мониторинга за пациентами с синдромом Дауна.</p></trans-abstract><kwd-group xml:lang="en"><kwd>Down syndrome</kwd><kwd>GATA1</kwd><kwd>transient abnormal myelopoiesis</kwd><kwd>myeloid leukemia associated with Down syndrome</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>синдром Дауна</kwd><kwd>GATA1</kwd><kwd>транзиторный аномальный миелопоэз</kwd><kwd>миелоидная лейкемия</kwd><kwd>ассоциированная с синдромом Дауна</kwd></kwd-group><funding-group/></article-meta></front><body></body><back><ref-list><ref id="B1"><label>1.</label><mixed-citation>De Graaf G., Buckley F., Skotko B.G. 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