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).
METHODS: 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.
METHODS: Tertiary clinical care.
METHODS: This study included 8 patients clinically diagnosed with TCS who were from 3 familial cases and 2 sporadic cases.
METHODS: 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.

Treacher Collins syndrome (TCS) is a congenital malformation of the craniofacial structures derived from the first and second pharyngeal arches. The craniofacial deformities are well described in the literature. However, little is known about whether there are associated extracraniofacial anomalies. A retrospective study was conducted using data from four craniofacial units. Medical charts were reviewed for the presence and type of extracraniofacial anomalies, as well as age at diagnosis. A possible correlation between the severity of the phenotype and the presence of extracraniofacial anomalies was assessed using the Hayashi classification. A total of 248 patients with TCS were identified; 240 were confirmed to have TCS, of whom 61 (25.4%) were diagnosed with one or more extracraniofacial anomalies. Ninety-five different extracraniofacial anomalies were found; vertebral (n=32) and cardiac (n=13) anomalies were most frequently seen, followed by reproductive system (n=11), central nervous system (n=7), and limb (n=7) anomalies. No correlations between tracts were found. Extracraniofacial anomalies were more prevalent in these patients with TCS compared to the general population (25.4% vs 0.001-2%, respectively). Furthermore, a positive trend was seen between the severity of the syndrome and the presence of extracraniofacial anomalies. A full clinical examination should be performed on any new TCS patient to detect any extracraniofacial anomalies on first encounter with the craniofacial team.