{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,23]],"date-time":"2026-07-23T17:04:26Z","timestamp":1784826266253,"version":"3.55.0"},"reference-count":36,"publisher":"SAGE Publications","license":[{"start":{"date-parts":[[2026,7,1]],"date-time":"2026-07-01T00:00:00Z","timestamp":1782864000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"},{"start":{"date-parts":[[2026,7,1]],"date-time":"2026-07-01T00:00:00Z","timestamp":1782864000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"funder":[{"DOI":"10.13039\/100011110","name":"UCB","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100011110","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Therapeutic Advances in Rare Disease"],"published-print":{"date-parts":[[2026,7]]},"abstract":"<jats:sec>\n                    <jats:title>Background:<\/jats:title>\n                    <jats:p>Thymidine kinase 2 deficiency (TK2d) is an ultra-rare autosomal recessive mitochondrial disease characterized by progressive myopathy.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objectives:<\/jats:title>\n                    <jats:p>To understand patient experiences and the impact of TK2d on patient quality of life (QoL), and to explore support needs.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design:<\/jats:title>\n                    <jats:p>A cross-sectional international online survey.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods:<\/jats:title>\n                    <jats:p>The survey for the Assessment of TK2d Patient Perspectives (ATP) study, co-created with patient advocates, included multiple-choice questions, verbal rating scales, and open free-text questions. Patients of all ages with a self-reported genetic diagnosis of TK2d were eligible to participate, either directly or through a caregiver proxy. The patient, caregiver proxy, or bereaved caregiver proxy answered questions on demographics, signs\/symptoms, impacts on health-related QoL (HRQoL), support needs, healthcare resource use, and overall experience of living with TK2d. Quantitative data were summarized with descriptive statistics. Qualitative data were analyzed using inductive thematic analysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results:<\/jats:title>\n                    <jats:p>Responses for 32 patients (24 patient and 8 caregiver proxy responses) were collected between September 2023 and February 2024. All patients experienced myopathic symptoms. The most frequently reported impact of TK2d was on patients\u2019 ability to perform basic activities of daily living (26\/32), including difficulties in walking (22\/32), eating\/swallowing (19\/32), and breathing (25\/32). The proportions of patients reporting a moderate or severe impact of breathing and walking difficulties on HRQoL, and the proportions requiring medical devices, were higher for those with an earlier age of TK2d symptom onset (\u2a7d2, vs &gt;2 to \u2a7d12, or &gt;12\u2009years). For most patients, TK2d also had a negative impact on mood, social and leisure activities, and employment\/education. Progressive loss of abilities, increasing dependency on others, and medical equipment use contributed to mental and emotional burdens.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion:<\/jats:title>\n                    <jats:p>These quantitative and qualitative analyses of patients\u2019 lived experiences highlight the substantial, progressive, and wide-ranging burden of TK2d.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1177\/26330040261469197","type":"journal-article","created":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T16:51:22Z","timestamp":1784652682000},"update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":0,"title":["Patients\u2019 lived experience of thymidine kinase 2 deficiency: the online survey-based assessment of TK2d patient perspectives study"],"prefix":"10.1177","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5781-9824","authenticated-orcid":false,"given":"Amel","family":"Karaa","sequence":"first","affiliation":[{"name":"Massachusetts General Hospital, Division of Genetics, Harvard Medical School, 175 Cambridge Street, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4608-9747","authenticated-orcid":false,"given":"Asha","family":"Hareendran","sequence":"additional","affiliation":[{"name":"UCB, Slough, Berkshire, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-3015-8704","authenticated-orcid":false,"given":"Katie","family":"Waller","sequence":"additional","affiliation":[{"name":"The Lily Foundation, Warlingham, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philip","family":"Yeske","sequence":"additional","affiliation":[{"name":"United Mitochondrial Disease Foundation, Pittsburgh, PA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexandra","family":"Morrison","sequence":"additional","affiliation":[{"name":"Rare Disease Research Partners, Amersham, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marnie","family":"Ross","sequence":"additional","affiliation":[{"name":"Rare Disease Research Partners, Amersham, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1396-5146","authenticated-orcid":false,"given":"Cristy","family":"Balcells","sequence":"additional","affiliation":[{"name":"UCB, Smyrna, GA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"179","published-online":{"date-parts":[[2026,7,21]]},"reference":[{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1038\/ng751"},{"key":"e_1_3_4_3_2","unstructured":"Wang J El-Hattab AW Wong LJC. TK2-related mitochondrial DNA maintenance defect myopathic form. In: Adam MP Feldman J Mirzaa GM et al. eds. GeneReviews\u00ae. Seattle: University of Washington 2018. https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK114628\/ (2018 accessed 1 April 2026)."},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.1212\/NXG.0000000000200138"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.1186\/s13023-019-1071-z"},{"key":"e_1_3_4_6_2","doi-asserted-by":"publisher","DOI":"10.1136\/jmedgenet-2017-105012"},{"key":"e_1_3_4_7_2","doi-asserted-by":"publisher","DOI":"10.3233\/JND-210786"},{"key":"e_1_3_4_8_2","doi-asserted-by":"publisher","DOI":"10.3390\/ijms231911002"},{"key":"e_1_3_4_9_2","doi-asserted-by":"crossref","unstructured":"Dom\u00ednguez-Gonz\u00e1lez C Osorio AN Ma Y et al. The disease course of untreated patients with thymidine kinase 2 deficiency (TK2d) aged >12 years at TK2d symptom onset: findings from the largest international TK2d dataset (P2-11.020). 2025; 104(7_Supplement_1): 2629.","DOI":"10.1212\/WNL.0000000000210473"},{"key":"e_1_3_4_10_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.mito.2022.10.003"},{"key":"e_1_3_4_11_2","doi-asserted-by":"publisher","DOI":"10.1186\/s13023-021-02030-w"},{"key":"e_1_3_4_12_2","article-title":"EPH140. Prevalence estimation of thymidine kinase 2 deficiency, an ultra-rare autosomal recessive mitochondrial disease","volume":"2023","author":"Ma Y","unstructured":"Ma Y, Hine M, Agne M, et al. EPH140. Prevalence estimation of thymidine kinase 2 deficiency, an ultra-rare autosomal recessive mitochondrial disease. ISPOR Europe 2023 Abstracts. Value in Health; 2023: S229.","journal-title":"ISPOR Europe 2023 Abstracts"},{"key":"e_1_3_4_13_2","doi-asserted-by":"publisher","DOI":"10.1212\/WNL.0000000000213908"},{"key":"e_1_3_4_14_2","unstructured":"UCB. U.S. Prescribing Information KYGEVVI\u00ae. FDA https:\/\/www.accessdata.fda.gov\/drugsatfda_docs\/label\/2025\/219792s000lbl.pdf (2025 accessed 7 November 2025)."},{"key":"e_1_3_4_15_2","unstructured":"UCB. Summary of product characteristics KYGEVVI\u00ae. EMA https:\/\/ec.europa.eu\/health\/documents\/community-register\/html\/h2013.htm (2026 Accessed 01 April 2026)."},{"key":"e_1_3_4_16_2","doi-asserted-by":"publisher","DOI":"10.1097\/WCO.0000000000000743"},{"key":"e_1_3_4_17_2","volume-title":"Presented at the Mitochondrial Medicine - Therapeutic Development Conference","author":"Balcells C","year":"2021","unstructured":"Balcells C, Wilkinson A, Harte S, et al. Living with thymidine kinase 2 deficiency (TK2d): Using insights and perspectives from patients and caregivers to help connect an ultra-rare community, improve disease awareness, and inform treatment management. Presented at the Mitochondrial Medicine - Therapeutic Development Conference, 30 November\u20132 December 2021."},{"key":"e_1_3_4_18_2","doi-asserted-by":"publisher","DOI":"10.1186\/s12955-017-0818-2"},{"key":"e_1_3_4_19_2","unstructured":"European Medicines Agency (EMA). Patient experience data in EU medicines development and regulatory decision-making Outcome of the workshop on 21st September 2022 https:\/\/www.ema.europa.Eu\/en\/documents\/other\/executive-summary-patient-experience-data-eu-medicines-development-and-regulatory-decision-making-workshop_en.pdf (accessed 22 April 2025)."},{"key":"e_1_3_4_20_2","unstructured":"US Food and Drug Administration (FDA). FDA patient-focused drug development guidance series for enhancing the incorporation of the patient\u2019s voice in medical product development and regulatory decision making 2025. https:\/\/www.fda.Gov\/drugs\/development-approval-process-drugs\/fda-patient-focused-drug-development-guidance-series-enhancing-incorporation-patients-voice-medical (2025 accessed 22 April 2025)."},{"key":"e_1_3_4_21_2","unstructured":"FDA The United Mitochondrial Disease Foundation (UMDF) MitoAction TK2 Cures. TK2d patient listening session\u2013Monday https:\/\/www.umdf.org\/tk2d-patient-listening-session-january-2022\/ (2022 accessed 11 October 2024)."},{"key":"e_1_3_4_22_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.mito.2022.10.003"},{"key":"e_1_3_4_23_2","doi-asserted-by":"publisher","DOI":"10.1080\/2159676X.2019.1628806"},{"key":"e_1_3_4_24_2","unstructured":"Lumivero. 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