Introduction

Treacher Collins syndrome is a rare disorder caused by genetic defects , resulting in  changes in physical appearance. It affects structures formed from the 1st and 2nd pharyngeal arches, such as eyes, ears, cheeks, maxilla and mandible of the mouth, and temporomandibular (jaw) joint.¹ Also called Franceschetti syndrome or mandibular dysostosis, this condition affects 1 in 50000 live births, either due to family history or genetic mutation.² This is an autosomal dominant disorder, which means that the child may inherit the faulty gene from one of the parents. A small percentage of children inherit the genes in an autosomal recessive manner( from both parents).

History

Treacher Collins Syndrome was first described in 1889 as a congenital neonatal deformity by George Andreas Berry. In 1900, an ophthalmologist named Edward Treacher Collins presented two patients with eye deformities in London.

In the 1940s, Adolphe Franceschetti did further research on  the disorder and published extensive reviews with his colleague David Klein. They characterised facial features and coined the term mandibulofacial dysostosis.³

Today, it is known in the United States and United Kingdom as Treacher Collins syndrome, in Europe as Franceschetti-Klein syndrome, and elsewhere as mandibulofacial dysostosis.

Clinical features

The most commonly affected gene is TCOF1, but other genes, such as POLR1C and POLR1D, may also be involved. It is characterised by underdevelopment  of the facial skeleton on both sides of the face, absence of the ears, down-slanting eyes, notched lower lids, sunken cheekbones, broad mouth, pointed nose tip, high arch palate and dental defects. It can also affect circulatory, pulmonary, urinary, and reproductive systems and cause spinal anomalies. Over 90% of affected people have hearing loss due to middle ear deformities, an underdeveloped facial skeleton(the maxilla and mandible), cleft lip and palate and obstructive sleep apnea. Many children develop life-threatening airway obstruction, feeding difficulties and malformation of the jaw.⁴ Changes in physical appearance can affect their psychological and mental well-being.

Classification

The variation in the features has led to multiple classification systems with different names. The two most common classification systems are Kaban-Pruzansky and OMENS/ OMENS plus

SAT classification includes skeletal, auricular and soft tissue classification.

The SAT and OMENS classifications provide a range from simple to complex skeletal, soft tissue, and neurological involvement. The Kaban-Pruzansky classification explains malformations involving the mandible, masticatory (chewing) muscles, and the temporomandibular joint (TMJ). Therefore, it is more useful for orthodontists and maxillofacial surgeons in the reconstruction of the mandible and TMJ. It involves four classes: Type 1, Type 2A, Type 2B, and Type 3.⁵

OMENS classification

History of classifications

1963-Longacre et al proposed a classification based on unilateral/ bilateral involvement of the external ear and presence or absence of facial deformity

1965 - Grabb proposed an anatomical classification based on the involvement of the ear, mandible, maxilla, zygoma, and temporal bone, and oral involvement.

Converse proposed a classification based on the involvement of the mandible, ear, soft tissue and bone. Edgerton and Marsh described four clinical groups based on the dominant pattern of dysplasia. The first phenotypic classification incorporated ocular and extracranial findings. In 1991, Vento used an alphanumeric coding system to classify patients based on the severity of deformity in specific structures.

The OMENS classification is an acronym where O= orbital alteration, M=mandibular deformity, E=ear deformity, N= nerve involvement and S = soft tissue alterations. David et al proposed alpha alphanumeric coding classification called SAT, where S= skeletal deformity, A= auricular alteration and T= soft tissue anomalies. Pruzansky proposed a classification based on progressive mandibular deficiency: grade 1- minimal mandibular hypoplasia, grade 2- deformed TMJ joint and displaced condyle, grade 3- absence of ramus and glenoid fossa. This was later modified by Kaban et al 

Type I- mandible and temporomandibular joint (TMJ) are present but hypoplastic, type IIa- mandibular ramus, condyle, and temporomandibular joint are present but hypoplastic and abnormal in shape, type IIb- mandibular ramus is hypoplastic and markedly abnormal in form and location, and with no articulation with the temporal bone, type III- ramus, condyle and temporomandibular joint are absent. Prahl Anderson introduced a system that incorporates deformity of craniofacial bony structures using 3D imaging, called the craniofacial deformity score and mandibular deformity score. Pruzansky and Kaban’s classification, based on mandibular anatomical involvement, is a practical and useful one of them all.

New classification(Pruzansky and Kabans)

• Type I- Hypoplastic temporomandibular joint(TMJ)
• Type II-
  • IIa- hypoplastic and abnormal shape of mandibular ramus, condyle and TMJ
  • IIb- mandibular ramus is hypoplastic and abnormal in form and location, being medial and anterior.
• Type III- absence of mandibular ramus
• Type IV- mandibular body hypoplasia

Nikkah D et al proposed Orbito-zygomatic skeletal deformities. The classification is designed to characterise the degree of deformity and as a guide to treatment planning.⁴

• Type 1: orbito-zygomatic complex present but dysplastic and hypoplastic 
• Type 2: a hypoplastic zygomatic body with a vestigial zygomatic temporal process and a dysplastic lateral orbital wall
• Type 3: a hypoplastic zygomatic body and dysplastic orbital wall, but absence of the zygomatic temporal process 
• Type 4: complete absence of the entire orbito-zygomatic complex

Diagnosis

Children with Treacher-Collins syndrome are diagnosed with their characteristic appearance. No specific diagnostic tests are needed. X-ray or MRI may be suggested to monitor bone growth pre- and post-treatment and to examine the internal structures of the ear alongside hearing tests to diagnose hearing loss.⁶ Molecular testing of genes can confirm the diagnosis.⁷

Support for people affected by treacher collins syndrome and their families

 Charities such as Contact or Treacher Collins Family Support Group are available for those who have children affected by Treacher Collins Syndrome. These services provide information, support, and advice, as well as parent/carer workshops and resource libraries, offering details on Treacher Collins Syndrome.

Summary

Children born with Treacher Collins syndrome are treated depending on the severity of their symptoms and how they impact bodily functions such as breathing, vision and hearing. A classification system facilitates accurate symptom diagnosis and comprehensive treatment planning through long-term monitoring, particularly during periods of growth in childhood and adolescence.¹⁰