Treacher Collins syndrome (TCS) also known as mandibulofacial dysostosis or Treacher Collins-Franceschetti syndrome is a disorder of craniofacial development with an estimated incidence of 1:50,000 live births.  The most common findings include downward slanting palpebral fissures and hypoplasia of the zygomatic complex and mandible. Additional findings may include microtia, malformation of the auricles and atresia of the external ear canals, anomalies of the middle ear ossicles resulting in conductive hearing loss, lower lid coloboma with paucity of lid lashes medial to the defect, macrostomia and cleft palate. TCS has variable penetrance. Postaxial acrofacial dysostosis (POADS) also known as Miller syndrome is a disorder with craniofacial and postaxial limb deformities. Craniofacial findings include cleft lip and/or palate, micrognathia, coloboma of the eyelids, and cup-shaped ears. Postaxial limb deformities consist of aplasia of fifth digits of the hand and feet with or without ulnar and fibular hypoplasia. Additional findings may include malar hypoplasia, renal abnormalities and supernumerary nipples. Mandibulofacial dysostosis, Guion-Almeida type (MFDGA) is characterized by progressive microcephaly, craniofacial anomalies, congenital heart defects, choanal atresia, developmental delay, conductive hearing loss and speech delay. Craniofacial findings include midface and malar hypoplasia, micrognathia, cleft palate, microtia, and dysplastic ears. Esophageal atresia has been reported in some patients. Acrofacial dysostosis 1, Nager type (AFD1) is characterized by downslanting palpebral fissures, lower lid coloboma, microcephaly and micrognathia with midface retrusion, cleft lip or palate, posteriorly rotated low set ears with conductive deafness and macrostomia. Upper limb abnormalities can include hypoplasia or aplasia of the radii and thumbs, syndactyly, clinodactyly, radioulnar synostosis, triphalangeal thumbs and phocomelia. Lower limb abnormalities including aplasia or hypoplasia of the toes have also been described.

Copy number variation (CNV) analysis of the Treacher Collins syndrome and related disorders genes using high density targeted (HDT) array is also offered as a panel. Additionally, CTGT offers a comprehensive test (both NGS panel and HDT array panel) for these genes. Panel genes are also offered as individual sequencing and deletion/duplication tests, unless otherwise indicated.

The Treacher Collins syndrome and related disorders NGS panel consists of six genes: DHODH, EFTUD2, POLR1C, POLR1D, SF3B4 and TCOF1.