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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="other" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Russian Journal of Child Neurology</journal-id><journal-title-group><journal-title xml:lang="en">Russian Journal of Child Neurology</journal-title><trans-title-group xml:lang="ru"><trans-title>Русский журнал детской неврологии</trans-title></trans-title-group></journal-title-group><issn publication-format="print">2073-8803</issn><issn publication-format="electronic">2412-9178</issn><publisher><publisher-name xml:lang="en">Publishing House ABV Press</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">453</article-id><article-id pub-id-type="doi">10.17650/2073-8803-2023-18-4-53-57</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></subject></subj-group></article-categories><title-group><article-title xml:lang="en">Mitochondrial disorders in patients with familial form of MERRF syndrome</article-title><trans-title-group xml:lang="ru"><trans-title>Митохондриальные нарушения у пациентов с семейной формой синдрома MERRF</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0006-0064-0448</contrib-id><name-alternatives><name xml:lang="en"><surname>Latypov</surname><given-names>A. Sh.</given-names></name><name xml:lang="ru"><surname>Латыпов</surname><given-names>А. Ш.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0002-4865-433X</contrib-id><name-alternatives><name xml:lang="en"><surname>Proskurina</surname><given-names>E. V.</given-names></name><name xml:lang="ru"><surname>Проскурина</surname><given-names>Е. В.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-8706-7317</contrib-id><name-alternatives><name xml:lang="en"><surname>Kotov</surname><given-names>S. V.</given-names></name><name xml:lang="ru"><surname>Котов</surname><given-names>С. В.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-4113-5799</contrib-id><name-alternatives><name xml:lang="en"><surname>Sidorova</surname><given-names>O. P.</given-names></name><name xml:lang="ru"><surname>Сидорова</surname><given-names>О. П.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><email>sidorovaop2019@mail.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-6374-9786</contrib-id><name-alternatives><name xml:lang="en"><surname>Vasilenko</surname><given-names>I. A.</given-names></name><name xml:lang="ru"><surname>Василенко</surname><given-names>И. А.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-6759-9121</contrib-id><name-alternatives><name xml:lang="en"><surname>Kassina</surname><given-names>D. V.</given-names></name><name xml:lang="ru"><surname>Кассина</surname><given-names>Д. В.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-2988-5706</contrib-id><name-alternatives><name xml:lang="en"><surname>Kotov</surname><given-names>A. S.</given-names></name><name xml:lang="ru"><surname>Котов</surname><given-names>А. С.</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>Build. 1, 61/2 Shchepkina St., Moscow 129110</p></bio><bio xml:lang="ru"><p>129110 Москва, ул. Щепкина, 61/2, корп. 1</p></bio><xref ref-type="aff" rid="aff1"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">M.F. Vladimirsky Moscow Regional Research Clinical Institute</institution></aff><aff><institution xml:lang="ru">ГБУЗ МО «Московский областной научно-исследовательский клинический институт им. М.Ф. Владимирского»</institution></aff></aff-alternatives><pub-date date-type="pub" iso-8601-date="2023-12-15" publication-format="electronic"><day>15</day><month>12</month><year>2023</year></pub-date><volume>18</volume><issue>4</issue><issue-title xml:lang="en"/><issue-title xml:lang="ru"/><fpage>53</fpage><lpage>57</lpage><history><date date-type="received" iso-8601-date="2024-01-03"><day>03</day><month>01</month><year>2024</year></date><date date-type="accepted" iso-8601-date="2024-01-03"><day>03</day><month>01</month><year>2024</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2023, ABV-Press</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2023, АБВ-пресс</copyright-statement><copyright-year>2023</copyright-year><copyright-holder xml:lang="en">ABV-Press</copyright-holder><copyright-holder xml:lang="ru">АБВ-пресс</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://rjdn.abvpress.ru/jour/about/editorialPolicies</ali:license_ref></license></permissions><self-uri xlink:href="https://rjdn.abvpress.ru/jour/article/view/453">https://rjdn.abvpress.ru/jour/article/view/453</self-uri><abstract xml:lang="en"><p>MERRF syndrome (myoclonic epilepsy ragged red fibres) belongs to the group of primary mitochondrial diseases and is characterized by a combination of myoclonic epilepsy and the phenomenon of ragged red fibres on muscle biopsy. The aim of this work is to study mitochondrial disorders in patients from a family with MERRF syndrome by determining the cytochemical activity of mitochondrial enzymes in peripheral blood lymphocytes and the level of lactate in the blood. Clinical cases of a 25-year-old sister and a 19-year-old brother with MERRF syndrome with the m.8344A&gt;G variant in MT-TK (tRNA (Lys)) with a blood heteroplasmy level of 50 % in the sister and homoplasmy in the brother are presented. Mitochondrial disorders were assessed by blood lactate levels and cytochemical studies of mitochondrial enzyme activity in peripheral blood lymphocytes. Pre-prandial blood lactate levels were elevated in both patients. After a carbohydrate load, it increased in the sister, and decreased in the brother. The sister had decreased activity of peripheral blood lymphocyte enzymes while taking levetiracetam, 100 mg of coenzyme Q10 and 100 mg of L-carnitine. The dose of energotropic drugs was increased, which led to an increase in the activity of mitochondrial enzymes. The brother had a compensatory increase in the level of succinate dehydrogenase and a decrease in the activity of other enzymes. The methods we used can be used in clinical practice to diagnose mitochondrial disorders and to adjust the dosage of energotropic drugs, which remain relevant due to the lack of effective gene therapy.</p></abstract><trans-abstract xml:lang="ru"><p>Синдром MERRF (myoclonic epilepsy ragged-red fibers) относится к группе первичных митохондриальных заболеваний, характеризуется сочетанием миоклонической эпилепсии и феномена рваных красных волокон при биопсии мышц. Цель работы – изучить митохондриальные нарушения у пациентов из семьи с синдромом MERRF с помощью определения цитохимической активности митохондриальных ферментов лимфоцитов в периферической крови и уровня лактата в крови.Представлены клинические случаи сестры 25 лет и брата 19 лет с синдромом MERRF с вариантом m.8344A&gt;G в MT-TK (тРНК (Lys)), с уровнем гетероплазмии в крови 50 % у сестры и гомоплазмией у брата. Митохондриальные нарушения оценивали с помощью определения уровня лактата в крови и цитохимического исследования активности митохондриальных ферментов в лимфоцитах периферической крови. Уровень лактата в крови до еды был повышен у обоих пациентов. После нагрузки углеводами у сестры он увеличивался, а у брата снижался. У сестры была снижена активность ферментов лимфоцитов периферической крови на фоне приема леветирацетама, 100 мг коэнзима Q10 и 100 мг L-карнитина. Доза энерготропных препаратов была увеличена, что привело к повышению активности митохондриальных ферментов. У брата было компенсаторное повышение уровня сукцинатдегидрогеназы и снижение активности остальных ферментов.Применяемые нами методики можно использовать в клинической практике для диагностики митохондриальных нарушений и коррекции дозировки энерготропных препаратов, остающихся актуальными ввиду отсутствия эффективной генотерапии.</p></trans-abstract><kwd-group xml:lang="en"><kwd>MERRF</kwd><kwd>cytochemical activity of mitochondrial enzymes</kwd><kwd>lactate</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>MERRF</kwd><kwd>цитохимическая активность митохондриальных ферментов</kwd><kwd>лактат</kwd></kwd-group><funding-group/></article-meta></front><body></body><back><ref-list><ref id="B1"><label>1.</label><citation-alternatives><mixed-citation xml:lang="en">Kurbatova O.V., Izmaylova T.D., Surkov A.N. et al. Mitochondrial dysfunction in children with hepatic forms of glycogen storage disease. 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