{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,29]],"date-time":"2025-08-29T00:03:50Z","timestamp":1756425830316,"version":"3.44.0"},"reference-count":28,"publisher":"BMJ","issue":"12","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2024,11,20]]},"published-print":{"date-parts":[[2024,12]]},"abstract":"<jats:p>Methaemoglobinemia is a potentially life-threatening condition in which the heme iron is oxidised from the ferrous (Fe<jats:sup>2+<\/jats:sup>) to the ferric (Fe<jats:sup>3+<\/jats:sup>) state, leading to a left shift of the oxygen-dissociation curve and impaired oxygen delivery to the tissues. It can be either acquired through exposure to certain drugs or chemicals or inherited due to genetic mutations affecting enzymes like cytochrome b5 reductase.<\/jats:p>\n               <jats:p>We report a case of an adolescent who presented with a persistent cough and unremarkable physical examination, making diagnosis challenging. A low SpO<jats:sub>2<\/jats:sub> level that did not improve with supplemental oxygen prompted further testing, leading to the diagnosis of methaemoglobinemia caused by cytochrome b5 reductase deficiency. The case highlights the complexities of diagnosing methaemoglobinemia, especially in the absence of classic symptoms like cyanosis. It underscores the importance of thorough clinical assessment in atypical cases and the need for heightened awareness of rare conditions.<\/jats:p>","DOI":"10.1136\/bcr-2024-263218","type":"journal-article","created":{"date-parts":[[2024,12,22]],"date-time":"2024-12-22T09:25:35Z","timestamp":1734859535000},"page":"e263218","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Methaemoglobinemia in paediatrics: a complex diagnostic journey"],"prefix":"10.1136","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-4123-5180","authenticated-orcid":false,"given":"In\u00eas","family":"Aires Martins","sequence":"first","affiliation":[{"name":"Pediatrics Department, Centro Hospitalar Universit\u00e1rio do Porto EPE Centro Materno-Infantil do Norte Dr Albino Aroso, Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Joana","family":"Carvalho Queir\u00f3s","sequence":"additional","affiliation":[{"name":"Pediatrics Department, Centro Hospitalar Universit\u00e1rio do Porto EPE Centro Materno-Infantil do Norte Dr Albino Aroso, Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Esmeralda","family":"Cleto","sequence":"additional","affiliation":[{"name":"Hematology Unit, Pediatrics Department, Centro Hospitalar Universit\u00e1rio do Porto EPE Centro Materno-Infantil do Norte Dr Albino Aroso, Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Telma","family":"Barbosa","sequence":"additional","affiliation":[{"name":"Pneumology Unit, Pediatrics Department, Centro Hospitalar Universit\u00e1rio do Porto EPE Centro Materno-Infantil do Norte Dr Albino Aroso, Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2024,12,22]]},"reference":[{"key":"2025082803222690000_17.12.e263218.1","doi-asserted-by":"publisher","DOI":"10.1378\/chest.07-2236"},{"key":"2025082803222690000_17.12.e263218.2","doi-asserted-by":"crossref","DOI":"10.1186\/s12887-021-02739-4","article-title":"Coughing children in family practice and primary care: a systematic review of prevalence, aetiology and prognosis","volume":"21","author":"Bergmann","year":"2021","journal-title":"BMC Pediatr"},{"key":"2025082803222690000_17.12.e263218.3","doi-asserted-by":"publisher","DOI":"10.1016\/j.chest.2020.01.042"},{"key":"2025082803222690000_17.12.e263218.4","doi-asserted-by":"publisher","DOI":"10.1136\/thoraxjnl-2015-207473"},{"key":"2025082803222690000_17.12.e263218.5","doi-asserted-by":"publisher","DOI":"10.1378\/chest.11-2725"},{"key":"2025082803222690000_17.12.e263218.6","doi-asserted-by":"crossref","first-page":"875","DOI":"10.1016\/j.chest.2016.12.025","article-title":"Use of Management Pathways or Algorithms in Children With Chronic Cough","volume":"151","author":"Chang","year":"2017","journal-title":"Chest"},{"key":"2025082803222690000_17.12.e263218.7","doi-asserted-by":"crossref","unstructured":"Sinha N , Lichak B , Thomas NJ , et al . 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