Clinical Otolaryngology. 2020;45:695–702. wileyonlinelibrary.com/journal/coa | 695 © 2020 John Wiley & Sons Ltd Received: 28 October 2019 | Revised: 23 April 2020 | Accepted: 27 April 2020 DOI: 10.1111/coa.13560 ORIGINAL ARTICLE Treacher Collins syndrome: A novel TCOF1 mutation and monopodial stapes Piranit Nik Kantaputra 1,2,3 | Kanich Tripuwabhrut 4 | Worrachet Intachai 1 | Bruce M. Carlson 5 | Natalina Quarto 6 | Chumpol Ngamphiw 7 | Sissades Tongsima 7 | Nuntigar Sonsuwan 8 1 Center of Excellence in Medical Genetics Research, Chiang Mai University, Chiang Mai, Thailand 2 Division of Pediatric Dentistry, Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand 3 Dentaland Clinic, Chiang Mai, Thailand 4 Division of Orthodontics, Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand 5 Department of Anatomy and Cell Biology, University of Michigan, Ann Arbor, MI, USA 6 Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA, USA 7 National Biobank of Thailand, National Center for Genetic Engineering and Biotechnology (BIOTEC), Thailand Science Park, Pathum Thani, Thailand 8 Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand Correspondence Piranit Nik Kantaputra, Division of Pediatric Dentistry, Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai 50200, Thailand. Email: dentaland17@gmail.com Funding information Faculty of Dentistry, Chiang Mai University, Grant/Award Number: NA; Dental Association of Thailand, Grant/Award Number: NA; Thailand Research Fund, Grant/Award Number: NA Abstract Treacher Collins syndrome (TCS: OMIM 154500) is an autosomal dominant craniofa- cial disorder belonging to the heterogeneous group of mandibulofacial dysostoses. Objective: To investigate four Treacher Collins syndrome patients of the Sgaw Karen family living in Thailand. Method: Clinical examination, hearing tests, lateral cephalometric analyses, Computed tomography, whole exome sequencing and Sanger direct sequencing were performed. Results: All of the patients affected with Treacher Collins syndrome carried a novel TCOF1 mutation (c.4138_4142del; p.Lys1380GlufsTer12), but clinically they did not have the typical facial gestalt of Treacher Collins syndrome, which includes down- ward-slanting palpebral fissures, colobomas of the lower eyelids, absence of eye- lashes medial to the colobomas, malformed pinnae, hypoplastic zygomatic bones and mandibular hypoplasia. Lateral cephalometric analyses identified short anterior and posterior cranial bases, and hypoplastic maxilla and mandible. Computed tomogra- phy showed fusion of malleus and incus, sclerotic mastoid, hypoplastic middle ear space with a soft tissue remnant, dehiscence of facial nerve and monopodial stapes. Conclusion: Treacher Collins syndrome in Sgaw Karen patients has not been previ- ously documented. This is the first report of monopodial stapes in a TCS patient who had a TCOF1 mutation. The absence of a common facial phenotype and/or the pres- ence of monopodial stapes may be the effects of this novel TCOF1 mutation.