UNASSIGNED: Treacher Collins syndrome (TCS) is a rare congenital disorder of craniofacial development characterized by numerous developmental anomalies that are restricted to the head and neck. Most TCS cases are inherited in an autosomal dominant manner. The diagnosis of TCS relies on clinical and radiographic findings. The four genes involved in TCS are TCOF1, POLR1D, POLR1C, and POLR1B.
UNASSIGNED: In this report, we present the case of a 7-year-old Moroccan boy who exhibited distinctive dysmorphic features, including coloboma and zygomatic bone hypoplasia. Upon genetic analysis, a mutation in the TCOF1 gene was identified, conclusively confirming the presence of Treacher Collins Syndrome. It is worthy that the correct etiological diagnosis was significantly delayed due to the initial misperception that the observed malformation syndrome was a result of drug teratogenicity.
UNASSIGNED: This case highlights the importance of seeking pharmacovigilance advice if any adverse event occurs following medication use. Furthermore, requesting a genetic consultation to establish a confirmed etiological diagnosis for any malformation syndrome can significantly reduce the protracted social and psychological suffering that patients and their families may endure.

OBJECTIVE: To study prenatal diagnosis of congenital Treacher Collins syndrome, an etiology of craniofacial abnormalities.
METHODS: We present a case of fetal craniofacial abnormalities identified by antepartum sonography screening in the third trimester (28 weeks); features of micrognathia, hypoplastic zygomatic arches and bilateral low-set microtia were detected. Due to the unknown severity of the craniofacial abnormalities and poor prognosis, the parents decided to terminate the fetus after through counselling. A normal female karyotype was detected. The parents consented to chromosome microarray analysis (CMA), which identified a de novo mutation of the TCS1 gene locus on chromosome 5.
CONCLUSIONS: Molecular CMA is an effective tool for prenatal diagnosis of congenital craniofacial abnormalities associated with Treacher Collins syndrome.

Treacher Collins syndrome (TCS) is associated with abnormal differentiation of the first and second pharyngeal arches, occurring during fetal development. Features of TCS include microtia with conductive hearing loss, slanting palpebral fissures with possibly coloboma of the lateral part of lower eyelids, midface hypoplasia, micrognathia as well as sporadically cleft palate and choanal atresia or stenosis. TCS occurs in the general population at a frequency of 1 in 50,000 live births. Four subtypes of Treacher Collins syndrome exist. TCS can be caused by pathogenic variants in the TCOF1, POLR1D, POLR1C and POLR1B genes. Genetically, the TCOF1 gene contains 27 exons which encodes the Treacle protein. In TCOF1, over 200 pathogenic variants have been identified, of which most are deletions leading to a frame-shift, that result in the formation of a termination codon. In the presented article, we review the genetics and phenotype of TCS as well as the management and surgical procedures utilized for treatment.

Összefoglaló. A Treacher Collins-szindróma a mandibulofacialis dysostosisok csoportjába tartozó kórkép. Főbb jellegzetességei a maxillaris és mandibularis dysostosis, az antimongoloid szemrések, az alsó szemhéj colobomája, illetve a vezetéses halláscsökkenés. A szindrómával járó tünetek egyénenként és családon belül is nagyon eltérőek lehetnek; legenyhébb formái csaknem észrevehetetlenek, míg a súlyosabb esetekben az életet veszélyeztető légúti szövődmények léphetnek fel. Hátterében az esetek döntő többségében a TCOF1-gén eltérései játszanak szerepet, mely eltérések autoszomális domináns módon öröklődnek. Esetbemutatásunk célja, hogy felhívjuk a figyelmet a genetikai vizsgálat elvégzésének fontosságára olyan, klinikailag jól felismerhető tünetegyüttes, mint a Treacher Collins-szindróma esetén. Bár a betegség a klinikai kép alapján diagnosztizálható, az ismétlődés kockázatát csak úgy tudjuk pontosan meghatározni, ha ismerjük a családtagok genotípusát. A bemutatott család több tagjánál kimutatható volt a TCOF1-gén mutációja, annak ellenére, hogy klinikai tünetük nem volt. A jelenség magyarázata az inkomplett penetrancia, azaz a hibás gén fenotípusosan nem kerül kifejeződésre. Orv Hetil. 2020; 161(52): 2201-2205. Summary. Treacher Collins syndrome belongs to the group of mandibulofacial dysostoses. Its main features are maxillary and mandibular dysostosis, downward-slanting palpebral fissures, coloboma of the lower eyelid and conductive hearing loss. The symptoms associated with the syndrome can vary greatly from individual to individual and within the family. In its mildest form, the syndrome is almost imperceptible, and when severe, life-threatening respiratory complication can occur. TCOF1 is the major gene involved with an autosomal dominant mode of inheritance. The purpose of our case study is to draw attention to the importance of performing genetic testing in a clinically recognizable disorder such as Treacher Collins syndrome. Although the disease can be diagnosed based on the clinical symptoms, the risk of recurrence can only be accurately determined if the genotype of the family members is known. Several members of the presented family had a mutation in the TCOF1 gene despite having no clinical symptoms. The explanation for this phenomenon is incomplete penetrance, i.e., the defective gene is not expressed in the phenotype. Orv Hetil. 2020; 161(52): 2201-2205.

Treacher Collins syndrome (TCS) is an autosomal dominant disorder of craniofacial development with an incidence of 1/50,000 live births. Mutations of the TCOF1 gene have been found to be responsible for most cases of this mandibulofacial disorder. Here we report TCS in an individual who has a heterozygous c.1021_1022delAG deletion in exon 7 of the TCOF1 gene (NG_011341.1). This is the second Turkish patient with a severe TCS phenotype resulting from a de novo c.1021_1022delAG mutation.