{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T12:30:15Z","timestamp":1787056215100,"version":"build-2736575974"},"reference-count":10,"publisher":"BMJ","issue":"8","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2026,7,28]]},"published-print":{"date-parts":[[2026,8]]},"abstract":"<jats:p>\n                    Transcobalamin deficiency is an autosomal recessive disease caused by pathogenic variants in the\n                    <jats:italic>TCN2<\/jats:italic>\n                    gene. It is a multisystem disorder, with haematological manifestations such as megaloblastic anaemia and pancytopenia. Neurological manifestations include ataxia, hypotonia and neuropathy. Gastrointestinal and immunological clinical presentations include diarrhoea, cytomegalovirus (CMV) colitis, failure to thrive and recurrent infections.\n                  <\/jats:p>\n                  <jats:p>\n                    We report a female toddler who initially presented at early infancy with severe failure to thrive, diarrhoea, CMV colitis and pancytopenia and was initially diagnosed with childhood myelodysplastic syndrome based on bone marrow examination and a strong family history in her cousins. Whole exome sequencing revealed a homozygous pathogenic variant, c.927_930del (p.(Cys309Trpfs*50)), in the\n                    <jats:italic>TCN2<\/jats:italic>\n                    , consistent with a diagnosis of autosomal recessive transcobalamin deficiency. Treatment with parenteral hydroxocobalamin resulted in dramatic improvement in her symptoms and resolved the myelodysplastic changes.\n                  <\/jats:p>","DOI":"10.1136\/bcr-2025-271492","type":"journal-article","created":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T11:55:26Z","timestamp":1787054126000},"page":"e271492","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Myelodysplasia uncovering transcobalamin deficiency"],"prefix":"10.1136","volume":"19","author":[{"given":"Khalsa","family":"Al Sulaimi","sequence":"first","affiliation":[{"name":"Oman Medical Speciality Board, Muscat, Oman"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Atheer","family":"Al Zaabi","sequence":"additional","affiliation":[{"name":"Pediatrics, Oman Medical Speciality Board, Muscat, Oman"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4275-4524","authenticated-orcid":false,"given":"Yasser","family":"Wali","sequence":"additional","affiliation":[{"name":"Department of Child Health, Sultan Qaboos University, Muscat, Oman"},{"name":"Alexandria University Faculty of Medicine, Alexandria, Egypt"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fathiya Qaboos","family":"Al Murshedi","sequence":"additional","affiliation":[{"name":"Genetics, Sultan Qaboos University Hospital, Seeb, Oman"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,8,18]]},"reference":[{"key":"2026081804551380000_19.8.e271492.1","doi-asserted-by":"crossref","first-page":"37","DOI":"10.4274\/tjh.galenos.2018.2018.0230","article-title":"Different Presentations of Patients with Transcobalamin II Deficiency: A Single-Center Experience from Turkey","volume":"36","author":"\u00dcnal","year":"2019","journal-title":"Turk J Haematol"},{"key":"2026081804551380000_19.8.e271492.2","doi-asserted-by":"crossref","DOI":"10.1136\/bcr-2019-232319","article-title":"Transcobalamin deficiency: vitamin B12 deficiency with normal serum B12 levels","volume":"12","author":"Khera","year":"2019","journal-title":"BMJ Case Rep"},{"key":"2026081804551380000_19.8.e271492.3","doi-asserted-by":"crossref","DOI":"10.1007\/s10545-011-9431-4","article-title":"Transcobalamin (TC) deficiency and newborn screening","volume":"35","author":"Prasad","year":"2012","journal-title":"J Inherit Metab Dis"},{"key":"2026081804551380000_19.8.e271492.4","doi-asserted-by":"crossref","first-page":"461","DOI":"10.1007\/s10545-013-9664-5","article-title":"Update on transcobalamin deficiency: clinical presentation, treatment and outcome","volume":"37","author":"Trakadis","year":"2014","journal-title":"J Inherit Metab Dis"},{"key":"2026081804551380000_19.8.e271492.5","doi-asserted-by":"publisher","DOI":"10.1007\/BF01955004"},{"key":"2026081804551380000_19.8.e271492.6","doi-asserted-by":"publisher","DOI":"10.1016\/j.ymgme.2009.06.003"},{"key":"2026081804551380000_19.8.e271492.7","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1097\/MPH.0000000000000685","article-title":"Seven Patients With Transcobalamin Deficiency Diagnosed Between 2010 and 2014: A Single-Center Experience","volume":"39","author":"Yildirim","year":"2017","journal-title":"J Pediatr Hematol Oncol"},{"key":"2026081804551380000_19.8.e271492.8","doi-asserted-by":"publisher","DOI":"10.1515\/jpem-2020-0096"},{"key":"2026081804551380000_19.8.e271492.9","doi-asserted-by":"crossref","first-page":"164","DOI":"10.1111\/ejh.12136","article-title":"A stepwise \u03b1-thalassemia screening strategy in high-prevalence areas","volume":"91","author":"Alkindi","year":"2013","journal-title":"Eur J Haematol"},{"key":"2026081804551380000_19.8.e271492.10","article-title":"Unmasking Vitamin B12 Deficiency Misdiagnosed as Myelodysplastic Syndrome","volume":"2024","author":"Jamil","year":"2024","journal-title":"Case Rep Hematol"}],"container-title":["BMJ Case Reports"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bcr-2025-271492","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T11:55:27Z","timestamp":1787054127000},"score":1,"resource":{"primary":{"URL":"https:\/\/casereports.bmj.com\/lookup\/doi\/10.1136\/bcr-2025-271492"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8]]},"references-count":10,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,8,18]]},"published-print":{"date-parts":[[2026,8]]}},"alternative-id":["10.1136\/bcr-2025-271492"],"URL":"https:\/\/doi.org\/10.1136\/bcr-2025-271492","relation":{},"ISSN":["1757-790X"],"issn-type":[{"value":"1757-790X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8]]}}}