Orbital volume and shape in Treacher Collins syndrome

Craniofacial and Upper Airway Development in Patients With Treacher Collins Syndrome

ABSTRACT

This study evaluated age-associated morphology changes in the cranial base, facial development, and upper airway of patients with Treacher Collins syndrome (TCS). A total of 33 preoperative computed tomographic images (TCS, n = 14; control, n = 19) were included in the study and divided into three age-related subgroups (2-6 years, 7-18 years, and older than 18 years). Linear, angular cephalometric measurements and upper airway volumes were collected. All measurements were analyzed using ProPlan CMF software (version 3.0; Materialize, Leuven, Belgium). The association between aging and upper airway morphology was analyzed. Compared to control subjects, TCS patients had a smaller cranial base, maxilla, and nose; they also had reduced upper airway volume compared to control subjects. The observed differences were most significant in patients between the ages of 7 and 18 years. This study used computed tomography-based three-dimensional analyses to provide a detailed description of age-related changes that occur in craniofacial measurements and upper airway volumes in children, adolescents, and young adult patients with TCS in China. These data can be used to evaluate individual patients with TCS and to select treatment to improve the growth of the craniofacial region.

Phenotype Analysis and Genetic Study of Chinese Patients With Treacher Collins Syndrome

OBJECTIVE

The aim of this study was to confirm the pathogenic variants, explore the genotype-phenotype correlation and characteristics of Chinese patients with Treacher Collins syndrome (TCS).

DESIGN

Clinical details of 3 TCS family cases and 2 sporadic cases were collected and analyzed. Whole-exome sequencing and Sanger sequencing were conducted to detect causative variants.

SETTING

Tertiary clinical care.

PATIENTS

This study included 8 patients clinically diagnosed with TCS who were from 3 familial cases and 2 sporadic cases.

MAIN OUTCOME MEASURES

When filtering the database, variants were saved as rare variants if their frequency were less than 0.005 in the 1000 Genomes Project Database, the Exome Aggregation Consortium (ExAC) browser, and the Novogene database, or they would be removed as common ones. The pathogenic variants identified were verified by polymerase chain reaction. The sequencing results were analyzed by Chromas 2.1 software.

RESULTS

Two novel pathogenic variants (NM_000356.3: c.537del and NM_000356.3: c.1965_1966dupGG) and 2 known pathogenic variants (NM_000356.3: c.1535del, NM_000356.3: c.4131_4135del) were identified within TCOF1 which are predicted to lead to premature termination codons resulting in a truncated protein. There was a known missense SNP (NM_015972.3: c.139G>A) within POLR1D. No phenotype-genotype correlation was observed. Instead, these 8 patients demonstrated the high genotypic and phenotypic heterogeneity of TCS.

CONCLUSIONS

This study expands on the pathogenic gene pool of Chinese patients with TCS. Besides the great variation among patients which is similar to international reports, Chinese patients have their own characteristics in clinical phenotype and pathogenesis mutations.

Early mandibular morphological differences in patients with FGFR2 and FGFR3-related syndromic craniosynostoses: A 3D comparative study

Syndromic craniosynostoses are defined by the premature fusion of one or more cranial and facial sutures, leading to skull vault deformation, and midfacial retrusion. More recently, mandibular shape modifications have been described in FGFR-related craniosynostoses, which represent almost 75% of the syndromic craniosynostoses. Here, further characterisation of the mandibular phenotype in FGFR-related craniosynostoses is provided in order to confirm mandibular shape modifications, as this could contribute to a better understanding of the involvement of the FGFR pathway in craniofacial development. The aim of our study was to analyse early mandibular morphology in a cohort of patients with FGFR2- (Crouzon and Apert) and FGFR3- (Muenke and Crouzonodermoskeletal) related syndromic craniosynostoses. We used a comparative geometric morphometric approach based on 3D imaging. Thirty-one anatomical landmarks and eleven curves with sliding semi-landmarks were defined to model the shape of the mandible. In total, 40 patients (12 with Crouzon, 12 with Apert, 12 with Muenke and 4 with Crouzonodermoskeletal syndromes) and 40 age and sex-matched controls were included (mean age: 13.7 months ±11.9). Mandibular shape differed significantly between controls and each patient group based on geometric morphometrics. Mandibular shape in FGFR2-craniosynostoses was characterized by open gonial angle, short ramus height, and high and prominent symphysis. Short ramus height appeared more pronounced in Apert than in Crouzon syndrome. Additionally, narrow inter-condylar and inter-gonial distances were observed in Crouzon syndrome. Mandibular shape in FGFR3-craniosynostoses was characterized by high and prominent symphysis and narrow inter-gonial distance. In addition, narrow condylar processes affected patients with Crouzonodermoskeletal syndrome. Statistical analysis of variance showed significant clustering of Apert and Crouzon, Crouzon and Muenke, and Apert and Muenke patients (p < 0.05). Our results confirm distinct mandibular shapes at early ages in FGFR2- (Crouzon and Apert syndromes) and FGFR3-related syndromic craniosynostoses (Muenke and Crouzonodermoskeletal syndromes) and reinforce the hypothesis of genotype-phenotype correspondence concerning mandibular morphology.

Orbital shape in intentional skull deformations and adult sagittal craniosynostoses

Intentional cranial deformations are the result of external mechanical forces exerted on the skull vault that modify the morphology of various craniofacial structures such as the skull base, the orbits and the zygoma. In this controlled study, we investigated the 3D shape of the orbital inner mould and the orbital volume in various types of intentional deformations and in adult non-operated scaphocephaly - the most common type of craniosynostosis - using dedicated morphometric methods. CT scans were performed on 32 adult skulls with intentional deformations, 21 adult skull with scaphocephaly and 17 non-deformed adult skulls from the collections of the Muséum national d'Histoire naturelle in Paris, France. The intentional deformations group included six skulls with Toulouse deformations, eight skulls with circumferential deformations and 18 skulls with antero-posterior deformations. Mean shape models were generated based on a semi-automatic segmentation technique. Orbits were then aligned and compared qualitatively and quantitatively using colour-coded distance maps and by computing the mean absolute distance, the Hausdorff distance, and the Dice similarity coefficient. Orbital symmetry was assessed after mirroring, superimposition and Dice similarity coefficient computation. We showed that orbital shapes were significantly and symmetrically modified in intentional deformations and scaphocephaly compared with non-deformed control skulls. Antero-posterior and circumferential deformations demonstrated a similar and severe orbital deformation pattern resulting in significant smaller orbital volumes. Scaphocephaly and Toulouse deformations had similar deformation patterns but had no effect on orbital volumes. This study showed that intentional deformations and scaphocephaly significantly interact with orbital growth. Our approach was nevertheless not sufficient to identify specific modifications caused by the different types of skull deformations or by scaphocephaly.