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The relationship between genetic disorders and oral health: Part VII.

Many genetic disorders manifest themselves with different expressions of oral disease. This may include a high frequency of dental decay, susceptibility to periodontal (gum) disease, premature loss of teeth, delayed eruption of teeth, congenitally missing teeth, and malformed, conically-shaped teeth. In addition, specific pathologies of the tongue, the jaw bone and the mucosa, and malformations such as common cleft lip and palate, are also observed and associated with genetic disorders.

The mouth will offer the clinician important clues for the diagnosis of several genetic diseases, Some oral-cavity findings may lead to early diagnosis of a genetic disorder, such as the typical gingival (gum) enlargement seen in mucolipidosis II. Other findings may serve as an early warning of a more complex disorder. For example, enlargement of one side of the tongue may indicate congenital hemihypertrophy. Because of these oral-cavity symptoms of genetic disorders, the dentist should be part of the team that makes the diagnosis, develops the treatment approach and manages the ongoing care of children with special needs.

TYPES OF GENETIC DISORDERS

It is generally understood that specific traits of individuals are the result of interactions between their genetic makeup ("nature") and their environment, including the intrauterine environment ("nurture"). By extension, the manifestations of a specific disorder-malformations, anomalies of the teeth, tongue, and other oral structures-come partly from "nature" and partly from "nurture." Genetic disorders are classified under three broad categories:

* Single locus, or Mendelian

These are disorders produced and regulated by a single gene. Although any one of them may be rare, in the aggregate they constitute a problem in public health. Examples of these are cystic fibrosis, sickle cell anemia and other hemoglobinopathies, hemophilia, achondroplasia and ectodermal dysplasia. They may be classified as autosomal dominant, autosomal recessive, X-linked dominant and X-linked recessive modes of inheritance.

* Chromosomal abnormalities

This group of disorders is characterized by abnormalities of the number and/or structure of chromosomes. Virtually all chromosomes are now associated with recognizable syndromes. Humans have 23 pairs of chromosomes, or 46 chromosomes. Twenty-two of these pairs are the autosomes, while the remaining pair, the X and Y chromosome, are the sex chromosomes. Down syndrome is an example of this category. Most people with Down syndrome have an extra chromosome 21; the disorder is also known as trisomy 21.

* Multifactorial disorders

This group reflects the interaction of genes and the environment. Cleft lip and palate, neural tube defects such as spina bifida, hip dislocation and several congenital heart diseases are all examples of disorders in this category. Relatives may exhibit the same or similar disorders.

ORODENTAL ASPECTS OF GENETIC DISORDERS

An increasing number of congenital and developmental anomalies of the mouth have been recognized as being associated with genetic disorders. In many cases the lips, gingiva (gums) and tongue are an integral part of the disorder, though in some they may be coincidental.

* Anomalies of the lips

Lip pits: Lip pits, usually bilateral and found on the surface of the lower lip, are associated with cleft lip and palate as symptoms of van der Woude syndrome. They represent outlets of small salivary or mucous glands. On some occasions the pit may be single and located near or on the mid-line. Van der Woude syndrome is autosomal dominant, so if one parent is affected with lower-lip pits, the risk of transmitting the disorder is 50 percent for each pregnancy.

Lip pigmentation: Peutz-Jeghers syndrome is a form of hereditary intestinal polyposis that may lead to colon cancer and is characterized by mucocutaneous (freckle-like) pigmentation of the lips and inner cheeks.

Lip nodules: In young people, small nodules on the lips may represent neuromas. The neuromas, which may also be visible on the eyelids, are associated with thyroid cancer in multiple endocrine neoplasia syndrome type 2B.

Cleft lip and palate: Cleft lip and palate is the most common congenital anomaly that affects the head and neck structures, with an overall incidence in the US of about 1 in 1,000 newborns. Most cases are multifactorial disorders with relatively low risk recurrence. However, in a significant number of cases, cleft lip and palate represent just one manifestation of a more complex genetic disorder. Indeed, more than 400 disorders may include cleft lip and palate. Cleft palate teams usually include a geneticist, who can evaluate each case.

Multi-center studies are underway, trying to determine the specific genetic cause of cleft lip and palate. Considerable research has also been done on preventive measures that may help to reduce the risk of having a child with cleft lip and palate. Preliminary results indicate that taking multivitamins and folic acid before and during the pregnancy may help to reduce occurrence of cleft lip and palate.

* Anomalies of the gingiva (gums)

Several disorders may affect the gums and also the bony sockets of the teeth. The gum diseases may range from gingivitis (inflammation of the gums) to periodontal disease, which involves destruction of bone and may lead to the loss of teeth.

Gingivitis: This disorder is inflammation of the marginal surface of the gums. The gums are enlarged, reddish in appearance and may bleed when touched or when using a toothbrush. Gingivitis is usually caused by poor oral hygiene, but mouth breathing may also be a factor. Oral hygiene at home will prevent most gingivitis; however, Down syndrome, Prader-Willi syndrome, and other disorders that include mental retardation call for assistance from the person's dentist.

Periodontitis: Periodontitis is a progressive deterioration of the support system of the tooth. A tooth may have more mobility than others and become loose. With the use of radiographs, the dentist can see the bone loss that eventually will lead to lost teeth unless opportune periodontal treatment is provided.

Both gingivitis and periodontitis occur as isolated oral health problems; however, they may also be associated with genetic disorders.

Down syndrome: Children with Down syndrome are especially susceptible to gingivitis and periodontal disease. Thus, it is important to develop and maintain good home oral hygiene practices and to schedule regular visits to the dentist.

Mucolipidosis II: This syndrome, also known as i cell disease, is characterized by short stature, coarse facial features, psychomotor retardation and gingival enlargement. The gingival enlargement is an early manifestation of slow progressive growth that may even impair closure of the mouth. The teeth seem to be slow to erupt; however, radiographs show that the crowns have come through but are practically buried in the enlarged gingival tissue. This characteristic has not been described in other mucolipidoses or in the related mucopolysachharidoses and is thus an excellent diagnostic clue.

Gingival fibromatosis: This condition shows enlarged, hard gingiva. Usually few teeth can be seen, and many are just buried inside the gums. It shows an autosomal dominant mode of inheritance. However, gingival fibromatosis may be associated with several syndromes. One is Ramon syndrome, which includes hypertricosis (abundant body hair), seizures, mental retardation and short stature.

* Anomalies of the tongue

Macroglossia: Macroglossia is a term used to describe a large tongue that protrudes from the mouth. It interferes with the normal functions of the oral cavity and may produce severe deformities. Possible effects of macroglossia include airway obstruction; noisy breathing; difficulty with chewing and swallowing; drooling; slurred speech; sizable spaces between the teeth; mandibular prognathism; dry, Crocked ulcerations of the tongue; and infections. Beckwith syndrome, Morquio syndrome and Down syndrome are among those that may exhibit macroglossia.

Ankyloglossia (tongue tie): This is characterized by shortness of the lingual frenula, which thus restricts movements of the tongue. The restriction does not impair speech or swallowing. In rare occurrences, surgical repair may be necessary.

Bifid tongue: Bifid tongue appears as a cleft in the middle of the tongue. The condition is a result of failure of the lateral tubercles of the tongue to fuse at the midline. Bifid tongue may be observed in orofacial digital syndrome. Surgical repair is needed.

Lobulated tongue: This condition is attributed to maldevelopment of the lateral tubercles of the tongue. The lobes generally are observed in the front portion of the tongue and may number two, three or four. Lobulated tongue has been associated with orofacial digital syndrome.

Tongue asymmetry: This condition is an enlargement and thickening of one side of the tongue. It is generally progressive and is usually noted when an infant has feeding problems. Asymmetric tongue is usually associated with congenital hemihypertrophy, a condition that will show itself with an asymmetric enlargement of one side of the body. Generally tongue asymmetry is the first visible sign of the disorder. Wilms tumors may be another manifestation of congenital hemihyperthrophy, and ultrasound studies will be needed to rule out the tumor.

Dr. Salinas is a Professor and Director of Craniofacial Genetics at Medical University of South Carolina and the Director of a Dental Program for the Diagnosis and Treatment of Children with Special Health Care Needs. His email is salinasc@musc.edu.

In the next part of EP's series on oral healthcare, Dr. Salinas will review anomalies of teeth and jaw that are associated with genetic disorders.
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Author:Salinas, Carlos F.
Publication:The Exceptional Parent
Geographic Code:1USA
Date:Dec 1, 2001
Words:1497
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