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The parents\u2019 complaint was that their child had language regression, did not respond to auditory stimuli and was presenting ASD behaviours. The parents were searching for information and a possible diagnosis and treatment for their child. Considering the child\u2019s history, an electroencephalogram (EEG) and a CT exam, as well as audiological and language assessments, were requested. The audiological assessment indicated normality. As for the language assessment, auditory agnosia and expressive deficits, language fluctuation, restricted sound production and sporadic word use, many of which were unintelligible, were verified. Regarding neurodevelopment, all areas were compromised and symptoms included irritability, motor excitation and impulsivity. There was no score for signs of ASD, although some behaviours could be observed. The child was diagnosed with Landau-Kleffner syndrome (LKS), a rare paediatric neurological disorder characterised by language regression and abnormal EEG activity. Although LKS is a rare condition, there is a need for greater awareness of this syndrome, particularly in light of language regression and suspicion of Acquired Hearing Loss.<\/jats:p>","DOI":"10.1136\/bcr-2025-268738","type":"journal-article","created":{"date-parts":[[2026,1,12]],"date-time":"2026-01-12T15:30:19Z","timestamp":1768231819000},"page":"e268738","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Diagnostic challenges in Landau-Kleffner syndrome"],"prefix":"10.1136","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9381-0680","authenticated-orcid":false,"given":"Dion\u00edsia","family":"Lam\u00f4nica","sequence":"first","affiliation":[{"name":"Speech-Language Pathology and Audiology, Bauru School of Dentistry - University of S\u00e3o Paulo, Bauru, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9953-1001","authenticated-orcid":false,"given":"Kriscia Gobi","family":"Rosa","sequence":"additional","affiliation":[{"name":"Speech-Language Pathology and Audiology, S\u00e3o Paulo State University, Marilia, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9937-7806","authenticated-orcid":false,"given":"Eduardo","family":"da Rocha","sequence":"additional","affiliation":[{"name":"Speech-Language Pathology and Audiology, Bauru School of Dentistry - University of S\u00e3o Paulo, Bauru, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-7350-2780","authenticated-orcid":false,"given":"Danielle","family":"Lemos","sequence":"additional","affiliation":[{"name":"Speech-Language Pathology and Audiology, Bauru School of Dentistry - University of S\u00e3o Paulo, Bauru, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9691-4672","authenticated-orcid":false,"given":"C\u00e9lia Maria","family":"Giacheti","sequence":"additional","affiliation":[{"name":"Speech-Language Pathology and Audiology, S\u00e3o Paulo State University, Marilia, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2026,1,12]]},"reference":[{"key":"2026011207301326000_19.1.e268738.1","unstructured":"Online Mendelian Inheritance in Man (OMIM) . #245570 \u2013 Epilepsy, focal, with speech disorder and with or without impaired intellectual development; FESD. 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