Acta Oto-Laryngologica
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Genetic Aspects of Some Orofacial Anomalies E. Dahl To cite this article: E. Dahl (1976) Genetic Aspects of Some Orofacial Anomalies, Acta OtoLaryngologica, 82:1-6, 226-229, DOI: 10.3109/00016487609120890 To link to this article: http://dx.doi.org/10.3109/00016487609120890
Published online: 08 Jul 2009.
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [RMIT University Library]
Date: 07 April 2016, At: 02:43
Acta Otolaryngol82: 226-229, 1976
GENETIC ASPECTS OF SOME OROFACIAL ANOMALIES
E. Dahl
Downloaded by [RMIT University Library] at 02:43 07 April 2016
From the Department of Orthodontics, Royal Dental College, Copenhagen, Denmark
portant sources of communication: the facial appearance and the organs of speech, hearing and vision. They represent a considerable medical and social problem. Some congenital craniofacial anomalies are caused by a genotype which expresses itself in virtually all environments, others by chromosome aberrations, and a few are caused by non-recurrent environmental damage. The The development of the dentition and the majority, however, is multifactorial, i.e. a craniofacial structures is considerably influ- combined action of deviations in several gene enced by genetic factors, and many anoma- positions and environmental factors. Even lies in this region display a hereditary pattern. within one clinical category, such as facial The conquest of nutritional and infectious clefts, some cases may have a major genetic diseases in infants in the developed countries component, and other cases, clinically inhave exposed the congenital anomalies as a distinguishable from them, may have a major major factor in childhood disease (Warkany, environmental cause. Therefore, no classifica1971). tion of the anomalies by their heredity is atThe exact prevalence of congenital cranio- tempted. facial anomalies is unknown. Only for cleft lip Clinical management of craniofacial anomaand palate are reliable incidence figures avail- lies often presents complex problems which able. From the centralized recording of cleft involve several professional disciplines. This deformities in Denmark the prevalence at birth is exemplified by the service given to cleft lip is estimated to be 2 per thousand (Fogh-An- and palate patients who need care from the dersen, 1966). According to this, approximate- specialties of plastic surgery, dentistry, otoly 600 children with facial clefts will be born rhinolaryngology and speech therapy. Exannually in Scandinavia. A centralized record- perience has shown that optimal rehabilitation ing of other congenital craniofacial anomalies is best obtained in centres where the number would highly facilitate the delineation of the of patients is sufficient to establish compreclinical problems and their appropriate man- hensive clinical experience and reliable data agement in these patients and would render for research. It is suggested that treatment it possible to observe variations in prevalence. and research in other craniofacial anomalies Congenital anomalies of the craniofacial would benefit from a similar integrated multistructures affect some of man’s most im- disciplinary approach. Abstract. The increased importance of congenital anomalies in childhood disease is stressed. It is suggested that treatment and research in congenital craniofacial anomalies would benefit from centralized registration. Their clinical management should be delegated to centres with a multidisciplinary team. Some problems related to genetic counselling and identification of microforms are illustrated by cleft lip and palate. An account is given of some orofacial anomalies.
Acta Otolaryngol82
Downloaded by [RMIT University Library] at 02:43 07 April 2016
Genetic aspects of some orofacial anomalies The final aim of the study of congenital anomalies is prevention. T o this end, aetiological factors must be found and their interaction explained. In most congenital disorders, the aetiology is unknown, and at present the most obvious prophylactic possibilities still seem to be the control of environmental teratogenic factors and genetic counselling. Some principal problems in genetic counselling can be illustrated by cleft lip and palate. Fogh-Andersen (1942) was able to show that cleft lip with or without cleft palate is genetically different from isolated cleft palate. The former is found more often in males and the latter more frequently in females. Only occasionally d o the two types occur in the same family, and the risk of recurrence is somewhat different. The common types of clefts are compatible with a multifactorial threshold model (Fraser, 1970). If one parent is affected, the risk for the first child is 3-5%. If the cleft is part of a syndrome, the mode of inheritance is often quite different. Over 100 syndromes are known (Gorlin et al., 1971; Gorlin & Cervenka, 1974) that involve clefts of the lip or palate. About one third of them are caused by major mutant genes. As an example may be mentioned the combination of cleft lip and palate and paramedian fistulae of the lower lip, which is transmitted as an autosomal dominant trait. This shows that accurate delineation of separate entities within categories can improve the quality of genetic counselling. A corresponding subdivision may be possible in a number of the classical syndromes. Another genetic approach is concerned with identifying those individuals in a population who carry a gene for a given affection, but who do not clearly demonstrate the phenotype for that gene. This implies that accurate definition of the phenotype is most important. In connection with cleft lip and palate a number of structural deviations related to the cleft region have been suggested as microforms of the cleft which should occur more frequently
227
in close relatives of persons with the defect than in the general population. This appears to be true for cleft uvula and submucous cleft palate, whereas it is questionable for nasal asymmetry and does not seem to be true for missing maxillary lateral incisors. Roentgen-cephalometric studies show that clefts of the secondary palate are often accompanied by characteristic changes in facial shape and that differences in this respect exist between different types of cleft (Dahl, 1970). Further studies are needed to reveal if such traits can discriminate genetic susceptibility. An account of some genetically determined orofacial anomalies is given below. Amelogenesis imperfecta, in which the tooth enamel exhibits varying types of defect, is an example of a hereditary anomaly localized to the dentition. Dentinogenesis imperfecta is inherited as an autosomal dominant trait with variable expressivity, but with a high degree of penetrance. It occurs as an independent trait or as part of the osteogenesis imperfecta syndrome. Most cases of hypodontia (congenital absence of some of the teeth) are probably determined by genetic factors. The condition is generally a local one, but may be one manifestation of a generalized ectodermal defect. Cleidocranial dysostosis is inherited as an autosomal dominant trait although spontaneous cases are quite common. The anomaly presents itself as an ossification defect, especially although not exclusively, of the membranous bones and mainly localized in the midline. The patients are usually short. The head is brachycephalic with frontal and parietal bossing. Closure of fontanelles and sutures is delayed and the lack of fusion of the frontal bones may extend into the nasal process resulting in a depression of the root of the nose. Wormian bones are formed in the suture lines. The mandibular symphysis may remain open. The oral manifestations include supernumerary teeth, and tooth eruption is delayed or absent. Submucous cleft palate may occur. There is aplasia or hypoplasia of the Acta Otolaryngol82
Downloaded by [RMIT University Library] at 02:43 07 April 2016
228
E. Dahl
clavicles, which permits a remarkable range of shoulder movement. Other skeletal deviations are reported, e.g. of the pelvic bones. Premature closure of sutures in the neurocranium and facial skeleton is the cause of a series of craniofacial anomalies. If localized in the neurocranium, they result in morphological changes, e.g. oxycephaly when the coronal suture is synostosed and scaphocephaly when the sagittal suture is prematurely closed. These simple cranial synostoses usually exhibit no genetic transmission. But in these cases, too, the combination with other anomalies can alter the pattern of inheritance. Thus, the combination of oxycephaly and syndactyly between the 2nd and 3rd fingers (Saethre-Chotzen syndrome) exhibits autosoma1 dominant inheritance (Kreiborg et al., 1972). In craniofacial dysosfosis (Crouzon syndrome), premature synostosis occurs in calvarian sutures, possibly in sutures of the cranial base, and in maxillary sutures. An autosomal dominant inheritance has been shown. The craniofacial growth is considerably disturbed. The synostosis may be progressive, and the deviations aggravate during growth. The head is brachycephalic; marked digital impressions are seen in radiographs of the skull; the sella turcica is large and the orbits are shallow, which contributes to the characteristic exophthalmos. The arrest of growth of the midfacial sutures results in an increasing disparity in the facial skeleton. Secondary involvement of the optic nerve and other neurological symptoms can be found. Otocraniofacial syndromes or first and second visceral arch anomalies include a wide spectrum of constellations of symptoms. Their proper delineation, developmental relations and causal mechanisms are still obscure. Mandibulofacial dysostosis (Treacher-Collin syndrome) is inherited as an autosomal dominant trait with variable expressivity and incomplete penetrance, but sporadic cases are not uncommon. The major features include hypoplasia of the malar bones, antimongoloid slant of palpebral fissures, coloboma of the Acta Otoluryngol82
lower lid, and dysplasia of the mandible. Ear anomalies, macrostomia and cleft palate may occur. The soft tissues are often poorly developed. The combination of symptoms and the degree of their manifestation may vary considerably. In its full expression the skeletal deviations include the sphenoid and the temporal bones (Poswillo, 1973; Dahl et al., 1975), which are not developed from the first or second branchial arch. The anomaly has been explained as a regional, embryological vascular defect. The characteristic facial shape is maintained relatively unchanged during growth. Hemifacial microsomia and Goldenhar syndrome are examples of unilateral otocraniofacial anomalies. They do not seem to show genetic transmission, and the symptoms are somewhat different from mandibulofacial dysostosis, e.g. there is often larger involvement of the outer ear.
ZUSAMMENFASSUNG Die steigernde Bedeutung von angeborenen Anomalien wird betont. Zentralisierte Registrierung ist fur die Behandlung und Forschung der angeborenen craniofacialen Anomalien sehr bedeutungsvoll. Die klinische Behandlung von diesen Anomalien sollte in Zentren mit einem multidisziplinaren Team stattfinden. Einige Probleme der genetischen Beratung und der Identifizierung von Mikroformen werden durch Lippen-Kiefer-Gaumenspalte illustriert. Einige orofaciale Anomalien werden besprochen.
REFERENCES Dahl, E. 1970. Craniofacial morphology in congenital clefts of the lip and palate. Acta Odont Scand 28, Suppl. 57. Dahl, E., Kreiborg, S. & Bjork, A. 1975. A morphologic description of a dry skull with mandibulofacial dysostosis. Scand J Dent R e s 83, 257. Fogh-Andersen, P. 1942. Inheritance of harelip and clefi palate. Nyt Nordisk Forlag, Copenhagen. - 1966. Incidence and etiology of clefts of lip, alveolus and palate in humans. In Schuchardt, K. (ed.). Treatment of patients with clefts of lip, alveolus and palate pp. 4-8. Georg Thieme Verlag, Stuttgart.
Genetic aspects of some orofacial anomalies
Kreiborg, S., Pruzansky, S. & Pashyan, H. 1972. The Saethre-Chotzen syndrome. Teratology 6,--287. Poswillo, D. 1973. The pathogenesis of the first and second branchial arch syndrome. Oral Surg 35, 302. Warkany, J. 1971. Congenitd malformations. Year Book Medical Publishers, Chicago.
Downloaded by [RMIT University Library] at 02:43 07 April 2016
Fraser, F. C. 1970. The genetics of cleft lip and cleft palate. Am J Hum Genet 22, 336. Gorlin, R. J. & Cervenka, J. 1974. Syndromes of facial clefting. Scand J Plast Reconstr Surg 8 , 13. Gorlin, R. J., Cervenka, J. & Pruzansky, S . 1971. Facial clefting and its syndromes. Birth Defects Orig Art Ser 7 . 3.
229
Acta Otolaryngol82
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Genetic Aspects of Some Orofacial Anomalies E. Dahl To cite this article: E. Dahl (1976) Genetic Aspects of Some Orofacial Anomalies, Acta OtoLaryngologica, 82:1-6, 226-229, DOI: 10.3109/00016487609120890 To link to this article: http://dx.doi.org/10.3109/00016487609120890
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 5
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [RMIT University Library]
Date: 07 April 2016, At: 02:43
Acta Otolaryngol82: 226-229, 1976
GENETIC ASPECTS OF SOME OROFACIAL ANOMALIES
E. Dahl
Downloaded by [RMIT University Library] at 02:43 07 April 2016
From the Department of Orthodontics, Royal Dental College, Copenhagen, Denmark
portant sources of communication: the facial appearance and the organs of speech, hearing and vision. They represent a considerable medical and social problem. Some congenital craniofacial anomalies are caused by a genotype which expresses itself in virtually all environments, others by chromosome aberrations, and a few are caused by non-recurrent environmental damage. The The development of the dentition and the majority, however, is multifactorial, i.e. a craniofacial structures is considerably influ- combined action of deviations in several gene enced by genetic factors, and many anoma- positions and environmental factors. Even lies in this region display a hereditary pattern. within one clinical category, such as facial The conquest of nutritional and infectious clefts, some cases may have a major genetic diseases in infants in the developed countries component, and other cases, clinically inhave exposed the congenital anomalies as a distinguishable from them, may have a major major factor in childhood disease (Warkany, environmental cause. Therefore, no classifica1971). tion of the anomalies by their heredity is atThe exact prevalence of congenital cranio- tempted. facial anomalies is unknown. Only for cleft lip Clinical management of craniofacial anomaand palate are reliable incidence figures avail- lies often presents complex problems which able. From the centralized recording of cleft involve several professional disciplines. This deformities in Denmark the prevalence at birth is exemplified by the service given to cleft lip is estimated to be 2 per thousand (Fogh-An- and palate patients who need care from the dersen, 1966). According to this, approximate- specialties of plastic surgery, dentistry, otoly 600 children with facial clefts will be born rhinolaryngology and speech therapy. Exannually in Scandinavia. A centralized record- perience has shown that optimal rehabilitation ing of other congenital craniofacial anomalies is best obtained in centres where the number would highly facilitate the delineation of the of patients is sufficient to establish compreclinical problems and their appropriate man- hensive clinical experience and reliable data agement in these patients and would render for research. It is suggested that treatment it possible to observe variations in prevalence. and research in other craniofacial anomalies Congenital anomalies of the craniofacial would benefit from a similar integrated multistructures affect some of man’s most im- disciplinary approach. Abstract. The increased importance of congenital anomalies in childhood disease is stressed. It is suggested that treatment and research in congenital craniofacial anomalies would benefit from centralized registration. Their clinical management should be delegated to centres with a multidisciplinary team. Some problems related to genetic counselling and identification of microforms are illustrated by cleft lip and palate. An account is given of some orofacial anomalies.
Acta Otolaryngol82
Downloaded by [RMIT University Library] at 02:43 07 April 2016
Genetic aspects of some orofacial anomalies The final aim of the study of congenital anomalies is prevention. T o this end, aetiological factors must be found and their interaction explained. In most congenital disorders, the aetiology is unknown, and at present the most obvious prophylactic possibilities still seem to be the control of environmental teratogenic factors and genetic counselling. Some principal problems in genetic counselling can be illustrated by cleft lip and palate. Fogh-Andersen (1942) was able to show that cleft lip with or without cleft palate is genetically different from isolated cleft palate. The former is found more often in males and the latter more frequently in females. Only occasionally d o the two types occur in the same family, and the risk of recurrence is somewhat different. The common types of clefts are compatible with a multifactorial threshold model (Fraser, 1970). If one parent is affected, the risk for the first child is 3-5%. If the cleft is part of a syndrome, the mode of inheritance is often quite different. Over 100 syndromes are known (Gorlin et al., 1971; Gorlin & Cervenka, 1974) that involve clefts of the lip or palate. About one third of them are caused by major mutant genes. As an example may be mentioned the combination of cleft lip and palate and paramedian fistulae of the lower lip, which is transmitted as an autosomal dominant trait. This shows that accurate delineation of separate entities within categories can improve the quality of genetic counselling. A corresponding subdivision may be possible in a number of the classical syndromes. Another genetic approach is concerned with identifying those individuals in a population who carry a gene for a given affection, but who do not clearly demonstrate the phenotype for that gene. This implies that accurate definition of the phenotype is most important. In connection with cleft lip and palate a number of structural deviations related to the cleft region have been suggested as microforms of the cleft which should occur more frequently
227
in close relatives of persons with the defect than in the general population. This appears to be true for cleft uvula and submucous cleft palate, whereas it is questionable for nasal asymmetry and does not seem to be true for missing maxillary lateral incisors. Roentgen-cephalometric studies show that clefts of the secondary palate are often accompanied by characteristic changes in facial shape and that differences in this respect exist between different types of cleft (Dahl, 1970). Further studies are needed to reveal if such traits can discriminate genetic susceptibility. An account of some genetically determined orofacial anomalies is given below. Amelogenesis imperfecta, in which the tooth enamel exhibits varying types of defect, is an example of a hereditary anomaly localized to the dentition. Dentinogenesis imperfecta is inherited as an autosomal dominant trait with variable expressivity, but with a high degree of penetrance. It occurs as an independent trait or as part of the osteogenesis imperfecta syndrome. Most cases of hypodontia (congenital absence of some of the teeth) are probably determined by genetic factors. The condition is generally a local one, but may be one manifestation of a generalized ectodermal defect. Cleidocranial dysostosis is inherited as an autosomal dominant trait although spontaneous cases are quite common. The anomaly presents itself as an ossification defect, especially although not exclusively, of the membranous bones and mainly localized in the midline. The patients are usually short. The head is brachycephalic with frontal and parietal bossing. Closure of fontanelles and sutures is delayed and the lack of fusion of the frontal bones may extend into the nasal process resulting in a depression of the root of the nose. Wormian bones are formed in the suture lines. The mandibular symphysis may remain open. The oral manifestations include supernumerary teeth, and tooth eruption is delayed or absent. Submucous cleft palate may occur. There is aplasia or hypoplasia of the Acta Otolaryngol82
Downloaded by [RMIT University Library] at 02:43 07 April 2016
228
E. Dahl
clavicles, which permits a remarkable range of shoulder movement. Other skeletal deviations are reported, e.g. of the pelvic bones. Premature closure of sutures in the neurocranium and facial skeleton is the cause of a series of craniofacial anomalies. If localized in the neurocranium, they result in morphological changes, e.g. oxycephaly when the coronal suture is synostosed and scaphocephaly when the sagittal suture is prematurely closed. These simple cranial synostoses usually exhibit no genetic transmission. But in these cases, too, the combination with other anomalies can alter the pattern of inheritance. Thus, the combination of oxycephaly and syndactyly between the 2nd and 3rd fingers (Saethre-Chotzen syndrome) exhibits autosoma1 dominant inheritance (Kreiborg et al., 1972). In craniofacial dysosfosis (Crouzon syndrome), premature synostosis occurs in calvarian sutures, possibly in sutures of the cranial base, and in maxillary sutures. An autosomal dominant inheritance has been shown. The craniofacial growth is considerably disturbed. The synostosis may be progressive, and the deviations aggravate during growth. The head is brachycephalic; marked digital impressions are seen in radiographs of the skull; the sella turcica is large and the orbits are shallow, which contributes to the characteristic exophthalmos. The arrest of growth of the midfacial sutures results in an increasing disparity in the facial skeleton. Secondary involvement of the optic nerve and other neurological symptoms can be found. Otocraniofacial syndromes or first and second visceral arch anomalies include a wide spectrum of constellations of symptoms. Their proper delineation, developmental relations and causal mechanisms are still obscure. Mandibulofacial dysostosis (Treacher-Collin syndrome) is inherited as an autosomal dominant trait with variable expressivity and incomplete penetrance, but sporadic cases are not uncommon. The major features include hypoplasia of the malar bones, antimongoloid slant of palpebral fissures, coloboma of the Acta Otoluryngol82
lower lid, and dysplasia of the mandible. Ear anomalies, macrostomia and cleft palate may occur. The soft tissues are often poorly developed. The combination of symptoms and the degree of their manifestation may vary considerably. In its full expression the skeletal deviations include the sphenoid and the temporal bones (Poswillo, 1973; Dahl et al., 1975), which are not developed from the first or second branchial arch. The anomaly has been explained as a regional, embryological vascular defect. The characteristic facial shape is maintained relatively unchanged during growth. Hemifacial microsomia and Goldenhar syndrome are examples of unilateral otocraniofacial anomalies. They do not seem to show genetic transmission, and the symptoms are somewhat different from mandibulofacial dysostosis, e.g. there is often larger involvement of the outer ear.
ZUSAMMENFASSUNG Die steigernde Bedeutung von angeborenen Anomalien wird betont. Zentralisierte Registrierung ist fur die Behandlung und Forschung der angeborenen craniofacialen Anomalien sehr bedeutungsvoll. Die klinische Behandlung von diesen Anomalien sollte in Zentren mit einem multidisziplinaren Team stattfinden. Einige Probleme der genetischen Beratung und der Identifizierung von Mikroformen werden durch Lippen-Kiefer-Gaumenspalte illustriert. Einige orofaciale Anomalien werden besprochen.
REFERENCES Dahl, E. 1970. Craniofacial morphology in congenital clefts of the lip and palate. Acta Odont Scand 28, Suppl. 57. Dahl, E., Kreiborg, S. & Bjork, A. 1975. A morphologic description of a dry skull with mandibulofacial dysostosis. Scand J Dent R e s 83, 257. Fogh-Andersen, P. 1942. Inheritance of harelip and clefi palate. Nyt Nordisk Forlag, Copenhagen. - 1966. Incidence and etiology of clefts of lip, alveolus and palate in humans. In Schuchardt, K. (ed.). Treatment of patients with clefts of lip, alveolus and palate pp. 4-8. Georg Thieme Verlag, Stuttgart.
Genetic aspects of some orofacial anomalies
Kreiborg, S., Pruzansky, S. & Pashyan, H. 1972. The Saethre-Chotzen syndrome. Teratology 6,--287. Poswillo, D. 1973. The pathogenesis of the first and second branchial arch syndrome. Oral Surg 35, 302. Warkany, J. 1971. Congenitd malformations. Year Book Medical Publishers, Chicago.
Downloaded by [RMIT University Library] at 02:43 07 April 2016
Fraser, F. C. 1970. The genetics of cleft lip and cleft palate. Am J Hum Genet 22, 336. Gorlin, R. J. & Cervenka, J. 1974. Syndromes of facial clefting. Scand J Plast Reconstr Surg 8 , 13. Gorlin, R. J., Cervenka, J. & Pruzansky, S . 1971. Facial clefting and its syndromes. Birth Defects Orig Art Ser 7 . 3.
229
Acta Otolaryngol82
