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Amelogenesis imperfecta

Reviewed February 2007

What is amelogenesis imperfecta?

Amelogenesis imperfecta is a disorder of tooth development. This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage. Other dental abnormalities are also possible. These defects, which vary among affected individuals, can affect both primary (baby) teeth and permanent teeth.

Researchers have described at least 14 forms of amelogenesis imperfecta. These types are distinguished by their specific dental abnormalities and by their pattern of inheritance.

How common is amelogenesis imperfecta?

The exact incidence of amelogenesis imperfecta is uncertain. Estimates vary widely, from 1 in 700 people in northern Sweden to 1 in 14,000 people in the United States.

What genes are related to amelogenesis imperfecta?

Mutations in the AMELX, ENAM, and MMP20 genes cause amelogenesis imperfecta.

The AMELX, ENAM, and MMP20 genes provide instructions for making proteins that are essential for normal tooth development. These proteins are involved in the formation of enamel, which is the hard, calcium-rich material that forms the protective outer layer of each tooth. Mutations in any of these genes alter the structure of these proteins or prevent the genes from making any protein at all. As a result, tooth enamel is abnormally thin or soft and may have a yellow or brown color. Teeth with defective enamel are weak and easily damaged.

In some cases, the genetic cause of amelogenesis imperfecta has not been identified. Researchers are working to find mutations in other genes that are responsible for this disorder.

Related Gene(s)

Changes in these genes are associated with amelogenesis imperfecta.

  • AMELX
  • ENAM
  • MMP20

How do people inherit amelogenesis imperfecta?

Amelogenesis imperfecta can have different inheritance patterns depending on the gene that is altered. Most cases are caused by mutations in the ENAM gene and are inherited in an autosomal dominant pattern. This type of inheritance means one copy of the altered gene in each cell is sufficient to cause the disorder.

Amelogenesis imperfecta is also inherited in an autosomal recessive pattern; this form of the disorder can result from mutations in the ENAM or MMP20 gene. Autosomal recessive inheritance means two copies of the gene in each cell are altered.

About 5 percent of amelogenesis imperfecta cases are caused by mutations in the AMELX gene and are inherited in an X-linked pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In most cases, males with X-linked amelogenesis imperfecta experience more severe dental abnormalities than females with this form of this condition.

Other cases of amelogenesis imperfecta result from new mutations in these genes and occur in people with no history of the disorder in their family.

Where can I find information about diagnosis or management of amelogenesis imperfecta?

These resources address the diagnosis or management of amelogenesis imperfecta and may include treatment providers.

  • Genetic Testing Registry: Amelogenesis imperfecta, type IC (http://www.ncbi.nlm.nih.gov/gtr/conditions/C2673923)
  • Genetic Testing Registry: AMELOGENESIS IMPERFECTA, TYPE IE (http://www.ncbi.nlm.nih.gov/gtr/conditions/C1845052)
  • Genetic Testing Registry: Amelogenesis imperfecta - hypoplastic autosomal dominant - local (http://www.ncbi.nlm.nih.gov/gtr/conditions/C0399368)
  • MedlinePlus Encyclopedia: Amelogenesis imperfecta (http://www.nlm.nih.gov/medlineplus/ency/article/001578.htm)
  • MedlinePlus Encyclopedia: Tooth - abnormal colors (http://www.nlm.nih.gov/medlineplus/ency/article/003065.htm)

You might also find information on the diagnosis or management of amelogenesis imperfecta in Educational resources (http://ghr.nlm.nih.gov/condition/amelogenesis-imperfecta/show/Educational+resources) and Patient support (http://ghr.nlm.nih.gov/condition/amelogenesis-imperfecta/show/Patient+support).

General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook. Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).

To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

Where can I find additional information about amelogenesis imperfecta?

You may find the following resources about amelogenesis imperfecta helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for amelogenesis imperfecta?

  • AI
  • Congenital enamel hypoplasia

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide) and How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about amelogenesis imperfecta?

Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/gard).

What glossary definitions help with understanding amelogenesis imperfecta?

amelogenesis ; autosomal ; autosomal dominant ; autosomal recessive ; calcium ; cell ; chromosome ; congenital ; enamel ; gene ; hypoplasia ; incidence ; inheritance ; inherited ; pattern of inheritance ; protein ; recessive ; sex chromosomes

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://ghr.nlm.nih.gov/glossary).

References

  • Aldred MJ, Savarirayan R, Crawford PJ. Amelogenesis imperfecta: a classification and catalogue for the 21st century. Oral Dis. 2003 Jan;9(1):19-23. Review. (http://www.ncbi.nlm.nih.gov/pubmed/12617253?dopt=Abstract)
  • Hart TC, Hart PS, Gorry MC, Michalec MD, Ryu OH, Uygur C, Ozdemir D, Firatli S, Aren G, Firatli E. Novel ENAM mutation responsible for autosomal recessive amelogenesis imperfecta and localised enamel defects. J Med Genet. 2003 Dec;40(12):900-6. (http://www.ncbi.nlm.nih.gov/pubmed/14684688?dopt=Abstract)
  • Kim JW, Seymen F, Lin BP, Kiziltan B, Gencay K, Simmer JP, Hu JC. ENAM mutations in autosomal-dominant amelogenesis imperfecta. J Dent Res. 2005 Mar;84(3):278-82. (http://www.ncbi.nlm.nih.gov/pubmed/15723871?dopt=Abstract)
  • Kim JW, Simmer JP, Hu YY, Lin BP, Boyd C, Wright JT, Yamada CJ, Rayes SK, Feigal RJ, Hu JC. Amelogenin p.M1T and p.W4S mutations underlying hypoplastic X-linked amelogenesis imperfecta. J Dent Res. 2004 May;83(5):378-83. (http://www.ncbi.nlm.nih.gov/pubmed/15111628?dopt=Abstract)
  • Nusier M, Yassin O, Hart TC, Samimi A, Wright JT. Phenotypic diversity and revision of the nomenclature for autosomal recessive amelogenesis imperfecta. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004 Feb;97(2):220-30. (http://www.ncbi.nlm.nih.gov/pubmed/14970781?dopt=Abstract)
  • Wright JT. The molecular etiologies and associated phenotypes of amelogenesis imperfecta. Am J Med Genet A. 2006 Dec 1;140(23):2547-55. Review. (http://www.ncbi.nlm.nih.gov/pubmed/16838342?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: February 2007
Published: April 28, 2015