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Amelogenesis imperfecta

Reviewed May 2015

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 (adult) 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. Additionally, amelogenesis imperfecta can occur alone without any other signs and symptoms or it can occur as part of a syndrome that affects multiple parts of the body.

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, MMP20, and FAM83H genes can cause amelogenesis imperfecta. The AMELX, ENAM, and MMP20 genes provide instructions for making proteins that are essential for normal tooth development. Most of 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. Although the function of the protein produced from the FAM83H gene is unknown, it is also believed to be involved in the formation of enamel. Mutations in any of these genes result in altered protein structure or prevent the production of any protein. 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.

Mutations in the genes described above account for only about half of all cases of the condition, with FAM83H gene mutations causing the majority of these cases. In the remaining cases, the genetic cause has not been identified. Researchers are working to find mutations in other genes that are involved in this disorder.

Related Gene(s)

Changes in these genes are associated with amelogenesis imperfecta.

  • AMELX
  • C4orf26
  • ENAM
  • FAM83H
  • ITGB6
  • KLK4
  • LAMB3
  • MMP20
  • SLC24A4
  • WDR72

How do people inherit amelogenesis imperfecta?

Amelogenesis imperfecta can have different inheritance patterns depending on the gene that is altered. Many cases are caused by mutations in the FAM83H 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. Some cases caused by mutations in the ENAM gene also have an autosomal dominant inheritance pattern.

Amelogenesis imperfecta can also be 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. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

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 gene mutations 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, hypocalcification type (http://www.ncbi.nlm.nih.gov/gtr/conditions/C0399376)
  • Genetic Testing Registry: Amelogenesis imperfecta, type 1E (http://www.ncbi.nlm.nih.gov/gtr/conditions/C1845052)
  • Genetic Testing Registry: Amelogenesis imperfecta, type IC (http://www.ncbi.nlm.nih.gov/gtr/conditions/C2673923)
  • 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 and 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 (https://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 ; inheritance pattern ; inherited ; pattern of inheritance ; protein ; recessive ; sex chromosomes ; syndrome

You may find definitions for these and many other terms in the Genetics Home Reference 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)
  • Chan HC, Estrella NM, Milkovich RN, Kim JW, Simmer JP, Hu JC. Target gene analyses of 39 amelogenesis imperfecta kindreds. Eur J Oral Sci. 2011 Dec;119 Suppl 1:311-23. doi: 10.1111/j.1600-0722.2011.00857.x. (http://www.ncbi.nlm.nih.gov/pubmed/22243262?dopt=Abstract)
  • Gasse B, Karayigit E, Mathieu E, Jung S, Garret A, Huckert M, Morkmued S, Schneider C, Vidal L, Hemmerlé J, Sire JY, Bloch-Zupan A. Homozygous and compound heterozygous MMP20 mutations in amelogenesis imperfecta. J Dent Res. 2013 Jul;92(7):598-603. doi: 10.1177/0022034513488393. Epub 2013 Apr 26. (http://www.ncbi.nlm.nih.gov/pubmed/23625376?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)
  • Hu JC, Chan HC, Simmer SG, Seymen F, Richardson AS, Hu Y, Milkovich RN, Estrella NM, Yildirim M, Bayram M, Chen CF, Simmer JP. Amelogenesis imperfecta in two families with defined AMELX deletions in ARHGAP6. PLoS One. 2012;7(12):e52052. doi: 10.1371/journal.pone.0052052. Epub 2012 Dec 14. (http://www.ncbi.nlm.nih.gov/pubmed/23251683?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)
  • Lee SK, Lee KE, Jeong TS, Hwang YH, Kim S, Hu JC, Simmer JP, Kim JW. FAM83H mutations cause ADHCAI and alter intracellular protein localization. J Dent Res. 2011 Mar;90(3):377-81. doi: 10.1177/0022034510389177. Epub 2010 Nov 30. (http://www.ncbi.nlm.nih.gov/pubmed/21118793?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, Torain M, Long K, Seow K, Crawford P, Aldred MJ, Hart PS, Hart TC. Amelogenesis imperfecta: genotype-phenotype studies in 71 families. Cells Tissues Organs. 2011;194(2-4):279-83. doi: 10.1159/000324339. Epub 2011 May 19. (http://www.ncbi.nlm.nih.gov/pubmed/21597265?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: May 2015
Published: September 1, 2015