{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T16:51:52Z","timestamp":1775580712416,"version":"3.50.1"},"reference-count":14,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2023,8,28]],"date-time":"2023-08-28T00:00:00Z","timestamp":1693180800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Medical University of Lublin","award":["DS 404"],"award-info":[{"award-number":["DS 404"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>The case reported presents a rare CD19\u2212 phenotype shift of an acute lymphoblastic leukaemia clone during relapse\/refractory ALL in a paediatric patient. We explore possible reasons for the promotion of CD19-negative cell selection, including discrete mutations and anti-CD19 treatment, which is gaining importance as targeted therapies such as blinatumomab enter standard treatment protocols. A 9-year-old male patient was diagnosed with B lymphocyte acute lymphoblastic leukaemia. Initial standard genetic analysis did not show significant chromosomal aberrations, and the patient underwent chemotherapy in line with the intermediate-risk protocol. After initially achieving remission, the disease relapsed, and the patient required hematopoietic stem cell transplantation (HSCT). In-depth retrospective microarray analysis performed at this point revealed additional risk factors, particularly a loss of function TP53 V173L mutation. A second recurrence was diagnosed which prompted targeted treatment application (blinatumomab) and subsequent HSCT. The third leukemic relapse, diagnosed shortly after the second HSCT, limited treatment options to last-resort CAR T-cell therapy in Germany. Subsequent immunophenotyping revealed insufficient CD19 expression by ALL clones and disqualified the patient from treatment. The patient died in October 2019 from disease progression. The case highlights the importance of in-depth molecular diagnostics and monitoring of relapse\/recurrent ALL cases to identify and manage risk factors during treatment.<\/jats:p>","DOI":"10.3390\/ijms241713322","type":"journal-article","created":{"date-parts":[[2023,8,28]],"date-time":"2023-08-28T03:45:42Z","timestamp":1693194342000},"page":"13322","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Relapse\/Refractory Paediatric B-ALL Case with CD19\u2212 Phenotype Switching Indicating the Importance of Appropriate Diagnostic Approach and Targeted Treatment Adjustment\u2014Case Report"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-0015-7956","authenticated-orcid":false,"given":"Anna","family":"Pra\u017cmo","sequence":"first","affiliation":[{"name":"Department of Pediatric Hematology, Oncology and Transplantology, Medical University of Lublin, 20-059 Lublin, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Patryk","family":"Jawoszek","sequence":"additional","affiliation":[{"name":"Doctoral School at Medical University of Lublin, 20-059 Lublin, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Borys","family":"Styka","sequence":"additional","affiliation":[{"name":"Independent Laboratory of Genetic Diagnostics, Medical University of Lublin, 20-059 Lublin, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8760-0775","authenticated-orcid":false,"given":"Monika","family":"Lejman","sequence":"additional","affiliation":[{"name":"Independent Laboratory of Genetic Diagnostics, Medical University of Lublin, 20-059 Lublin, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Agnieszka","family":"Zaucha-Pra\u017cmo","sequence":"additional","affiliation":[{"name":"Department of Pediatric Hematology, Oncology and Transplantology, Medical University of Lublin, 20-059 Lublin, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,8,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e577","DOI":"10.1038\/bcj.2017.53","article-title":"Acute lymphoblastic leukemia: A comprehensive review and 2017 update","volume":"7","author":"Terwilliger","year":"2017","journal-title":"Blood Cancer J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1146","DOI":"10.1016\/S0140-6736(19)33018-1","article-title":"Acute lymphoblastic leukaemia","volume":"395","author":"Malard","year":"2020","journal-title":"Lancet"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"481","DOI":"10.1182\/blood.V79.2.481.481","article-title":"Changing antigen receptor gene rearrangements in a case of early pre-B cell leukemia: Evidence for a tumor progenitor cell with stem cell features and implications for monitoring residual disease","volume":"79","author":"Tycko","year":"1992","journal-title":"Blood"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2173","DOI":"10.1182\/blood.2021012727","article-title":"Impact of high-risk cytogenetics on outcomes for children and young adults receiving CD19-directed CAR T-cell therapy","volume":"139","author":"Leahy","year":"2022","journal-title":"Blood"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"836","DOI":"10.1056\/NEJMoa1609783","article-title":"Blinatumomab versus Chemotherapy for Advanced Acute Lymphoblastic Leukemia","volume":"376","author":"Kantarjian","year":"2017","journal-title":"N. 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