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Disease Profile

Amelogenesis imperfecta

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

Infancy

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ICD-10

K00.5

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Categories

Congenital and Genetic Diseases

Summary

Amelogenesis imperfecta (AI) (amelogenesis - enamel formation; imperfecta imperfect) is a disorder that affects the structure and appearance of the enamel of the teeth. This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage with early tooth decay and loss. These dental problems, which vary among affected individuals, can affect both primary (baby) teeth and permanent teeth. People with this disease my also have problems involving the tissues surrounding teeth (periodontal tissues) such as gums, cementum, ligaments, and alveolar bones in which the tooth root rests. Teeth are also sensitive to either hot or cold exposures, and sometimes both. Severe and continuous pain due to exposed dentin resulting from the enamel defect is present in some cases.[1][2][3]

There are 4 main types of AI that are classified based on the symptoms, X-rays appearance and type of enamel defect. The main types are: hypoplastic (type I); hypomaturation (type II); hypocalcified (type III); and hypomaturation/hypoplasia/taurodontism (type IV). These 4 types are divided further into 17 or 18 subtypes, which are distinguished by their specific genetic cause and by their pattern of inheritance.[2][3] AI can be inherited in an autosomal dominant, autosomal recessive or X-linked recessive pattern.[1] Treatment may include dentures that cap the teeth (full crown restorations), orthodontic treatment, special toothpaste for the tooth sensitivity, and good oral hygiene.[3]

Symptoms

In general, both the primary and permanent teeth are affected. The enamel tends to be soft and weak, and the teeth appear yellow and damage easily.[2] 

The defects associated with amelogeneis imperfecta are highly variable and include abnormalities classified as hypoplastic (defects in the amount of enamel), hypomaturation (defect in the final growth and development of the tooth enamel), and hypocalcification (defect in the initial stage of enamel formation followed by defective tooth growth). The enamel in the hypomaturation and hypocalcification types is not mineralized and is thus described as hypomineralized.[2] 

Traditionally, the diagnosis and classification of amelogenesis imperfecta is based on the clinical presentation and the mode of inheritance. There are four principal types based on the defects in the tooth enamel. These types are subdivided into 14 different subtypes based on the clinical presentation and the mode of inheritance.[2] 

Detailed information about the signs and symptoms associated with the four major types of amelogenesis imperfecta is available from the UNC School of Dentistry.

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Yellow-brown discoloration of the teeth
Yellow-brown discolored teeth
0006286
30%-79% of people have these symptoms
Anterior open bite
0200095
Fragile teeth
0025124
Hypocalcification of dental enamel
Decreased enamel calcification
Poorly calcified tooth enamel

[ more ]

0011084
Hypomature dental enamel
0011085
Hypoplasia of dental enamel
Underdeveloped teeth enamel
0006297
Impaired mastication
Chewing difficulties
Chewing difficulty
Difficulty chewing

[ more ]

0005216
5%-29% of people have these symptoms
Abnormal jaw morphology
0030791
Abnormality of dentin
Abnormal dentin
0010299
Multiple unerupted teeth
Multiple non-erupting teeth
0006283
Taurodontia
0000679
Widely spaced teeth
Wide-spaced teeth
Widely-spaced teeth

[ more ]

0000687

Cause

Amelogenesis imperfecta is caused by mutations in the AMELX, ENAM, and MMP20 genes. These 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.[1]

In some cases, the genetic cause of amelogenesis imperfecta can not been identified. Researchers are working to find mutations in other genes that are responsible for this disorder.[1]

Click on each gene name to learn more about the role it plays in the development of tooth enamel.

Diagnosis

A dentist can identify and diagnose amelogenesis imperfecta on the basis of the patient's family history and the signs and symptoms present in the affected individual.[4]

Extraoral X-rays (X-rays taken outside the mouth) can reveal the presence of teeth that never erupted or that were absorbed. Intraoral X-rays (X-rays taken inside the mouth) show contrast between the enamel and dentin in cases in which mineralization is affected.[4]

Genetic testing is available for the genes AMELX, ENAM, and MMP20. You can visit the Genetic Testing Registry to locate laboratories performing genetic testing for these genes.[1]

The American Academy of Pediatric Dentistry is a source of information to find a pediatric dentist. The National Dental Association can also assist people in locating a dentist.

Treatment

Treatment depends on the type of amelogenesis imperfecta, the age of the affected person, and the type and severity of enamel abnormality.[1891][2] Treatments include preventative measures, various types of crowns, as well as tooth implants or dentures, orthodontic, peirodontal and restorative treatment.[5][4] The social and emotional impact of this condition should also be addressed.[4]

Detailed information on the treatment of amelogenesis imperfecta is available from the UNC School of Dentistry.

Organizations

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Organizations Providing General Support

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
      • Genetics Home Reference (GHR) contains information on Amelogenesis imperfecta. This website is maintained by the National Library of Medicine.
      • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

        In-Depth Information

        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) lists the subtypes and associated genes for Amelogenesis imperfecta in a table called Phenotypic Series. Each entry in OMIM includes a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Amelogenesis imperfecta. Click on the link to view a sample search on this topic.

          References

          1. Amelogenesis imperfecta. Genetics Home Reference (GHR). May 2015; https://ghr.nlm.nih.gov/condition/amelogenesis-imperfecta.
          2. Wright JT. Amelogenesis Imperfecta. Developmental Defects of the Teeth. https://www.dentistry.unc.edu/dentalprofessionals/resources/defects/ai/.
          3. Amelogenesis Imperfecta. National Organization for Rare Diseases (NORD). 2018; https://rarediseases.org/rare-diseases/amelogenesis-imperfecta/.
          4. Crawford PJM, Aldred M & Bloch-Zupan A. Amelogenesis imperfecta. Orphanet. April, 2007; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=88661.
          5. Naik M & Bansal S.. Diagnosis, Treatment Planning, and Full-mouth Rehabilitation in a Case of Amelogenesis Imperfecta. Contemporary Clinical Dentistry. 2018; 9(1):1-25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5863396/.
          6. Leung VW, Low B, Yang Y & Botelho MG. Oral Rehabilitation of Young Adult with Amelogenesis Imperfecta. J Contemp Dent Pract. May 1, 2018; 19(5):599-604. https://www.ncbi.nlm.nih.gov/pubmed/29807973.

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