Assessment of craniofacial and dental characteristics in individuals with treacher collins syndrome. A review

Abstract

Treacher Collins Syndrome (TCS) is a genetic disorder with predominantly autosomal dominant inheritance, associated with different mutations in specific genes. This review aimed to evaluate the facial, temporomandibular, zygomatic and bucco-dental phenotype in TCS individuals, and describe surgical and non-surgical solutions for each case in order to improve the quality of life of these individuals. A review of the literature on the craniofacial characteristics of the TCS was carried out, using the PICO strategy, and then a systematic search method was performed in Medline, Scopus, LILACS and SCIELO databases, identifying articles of impact and relevance until 10 June 2020, 240 articles were recovered and only 35 fulfilled the selection criteria. We found the main craniofacial and oral morphological characteristics of these individuals, and the possible functional alterations inducing repercussion in the stomatognathic apparatus. Among other characteristics, the most representative include hypoplasia in the zygomatic and mandibular complex, which can cause difficulty in breathing and feeding. In some cases, cleft palate and malocclusions such as anterior open bite may lead to Angle’s Class II malocclusion, sometimes causing problems in the temporomandibular joint. In conclusion, individuals with TCS have specific craniofacial features including maxillary hypoplasia, altered orbital zones, mandibular retrognathia, and temporomandibular disorders. Oral deformities produce to a higher prevalence of caries and calculus formation because of poor hygiene due to the malformations present in these patients.

Introduction

Treacher Collins Syndrome (TCS) is an autosomal dominant disorder with specific features in craniofacial growth and development. It bears this name thanks to Edward Treacher Collins, who described its characteristics in the year 1900, after which it was classified as mandibulofacial dysostosis by Franceschetti and Klein in 1949 [1], [2], [3].

The incidence of TCS is about one in every 50,000 births, although it is believed that between 60% of cases occur as a mutation that occurs for the first time in a family without altered genetic inheritance while the rest for specific mutations of family antecedents. In addition, it is presumed that the age of the parents is an important risk factor for this mutation [2], [4], [5]. The most common mode of inheritance is the dominant autosomic and the gene involved in its pathogenesis has been located on chromosome 5 and is called Treacher Collins-Franceschetti Syndrome 1 TCOF1 (63–93 %). But they are also related in less provided other genes such as Polymerase RNA I Polypeptide D POLR1D (6%) y Polymerase RNA I Polypeptide C POLR1C (1,2%) [3], [6].

TCS is characterized by the presence of bilateral asymmetric abnormalities. Individuals with TCS present a convex facial profile with a prominent back of the nose and a hypoplasia in the zygomatic complex and jaw, which can cause significant difficulties in feeding and with the proper functioning of the airways [7]. In some cases there is the presence of cleft palate and malocclusions such as anterior open bite and a tendency to Angle’s Class II malocclusion and a steep occlusal plane [8]. The ears may be absent or malformed, and hearing is affected as a result of varying degrees of hypoplasia of the ear canals and the bones of the middle ear [1], [6], [7]. A lateral downward slant of the palpebral fissures and coloboma of the lower eyelids also is frequently perceived in the eyes [6], [7].

Early detection and treatment can improve the quality of life of these patients, as many also have psychological problems and may even be exposed to bullying because of these malformations, and the subsequent possible need for psychological support [9]. Several studies have reported that the most frequent characteristics of this condition are mild to severe malar hypoplasia with asymmetries on the sides, ectopic tooth eruptions and usually a cleft palate is present. Nonetheless, more research is needed to confirm these results. Moreover, there are few review articles on TCS, with the latest having been published in 2016 [10]. Therefore, the aim of this review was to evaluate and differentiate the facial, temporomandibular, zygomatic and bucco-dental phenotype of individuals with TCS, and describe surgical and non-surgical solutions for each case in order to improve the quality of life of these individuals.