Treacher Collins syndrome.

Although Thomson [1] and Toynbee [2] likely first described the entity now known as Treacher Collins syndrome, Treacher Collins [3] first characterized it, and thus the syndrome bears his name. This condition, which is also referred to as mandibulofacial dysostosis, consists of craniofacial anomalies, cleft palate, and deafness. The facial anomalies, which are usually bilateral and symmetric, consist of down-slanting palpebral fissures, colobomata of the lower eyelid, scanty lower eyelashes, malar hypoplasia, and micro- or retrognathia. There is a palatal cleft in 35% of patients, and an additional 30 to 40% have congenital palatopharyngeal incompetence. [4,5] Ear anomalies are common and vary from minor malformations to severe microtia. Hearing loss is common, and can occur secondary to atresia of the auditory canals or ossicular malformation of the middle ear.

Perhaps the most life-threatening concomitant morbidities in patients with Treacher Collins syndrome are respiratory problems and respiratory failure. Initially, these conditions were thought to be secondary to glossoptosis; more recently, it has been determined that the anatomy of the airway plays a major role in determining the risk of airway compromise. Patients with Treacher Collins syndrome might have basicranial kyphosis, narrowing of the pharynx, and severe microretrognathia with deficient ramal height. [6,7]

Treacher Collins syndrome is inherited in an autosomal-dominant fashion, with as many as half of all cases attributable to a new mutation. Its variability of expression is rather wide, and some affected individuals have virtually no overt clinical manifestations. Thus, genetic counseling is rather difficult in the case of a child with Treacher Collins who is born to apparently unaffected parents. Recently, however, the causative gene has been identified and sequenced. [8] The responsible gene is TCOF1 (with the gene product called treacle). Its map location is 5q31.3-33.3. Identification of its location facilitates the use of linkage analysis in cases of possible reduced penetrance of the phenotype.

From Spectrum Health Genetics Services, Grand Rapids, Mich.

References

(1.) Thomson A. Notice of several cases of malformation of the external ear, together with experiments on the state of hearing in such persons. Monthly J Med Sci 1846;7:420.

(2.) Toynbee J. Description of a congenital malformation in the ears of a child. Monthly J Med Sci 1847;1:738-9.

(3.) Treacher Collins E. Case with symmetrical congenital notches in the Outer part of each lid and defective development of the malar bones. Trans Ophthalmol Soc UK 1900;20:190-2.

(4.) Gorlin RJ, Toriello HV, Cohen MM Jr. Hereditary Hearing Loss and Its Syndromes. New York: Oxford Press, 1995:62-5.

(5.) Dixon MJ. Treacher Collins syndrome. Hum Mol Genet 1996;5:1391-6.

(6.) Shapira J, Gleicher H, Moskovitz M, Peretz B. Respiratory arrest in Treacher-Collins syndrome: Implications for dental management: Case report. Pediatr Dent 1996;18:242-4.

(7.) Arvystas M, Shprintzen RJ. Craniofacial morphology in Treacher Collins syndrome. Cleft Palate Craniofac J 1991;28:226-31.

(8.) Dixon J, Edwards SJ, Anderson I, et al. Identification of the complete coding sequence and genomic organization of the Treacher Collins syndrome gene. Genome Res 1997;7:223-34.