Your QuestionMy family and I have a genetic tooth disorder, and I am convinced it is amelogenesis imperfecta (AI). Is it possible to prevent my children from inheriting this condition? Are there any treatments for those already affected?
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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.
Amelogenesis imperfecta can have different patterns of inheritance, 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 may 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.
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.
If an affected individual has a known mutation in one of the genes associated with this condition, it may be possible to test for the condition during pregnancy using fetal DNA obtained through chorionic villus sampling (CVS) or amniocentesis. Another form of genetic testing, called preimplantation genetic diagnosis (PGD), could potentially be used if a mutation has been identified in a family. To perform PGD, a couple must first undergo in vitro fertilization (IVF). One cell is removed from each of the resulting embryos and is used to perform DNA testing. Only the embryos that test negative for the mutation are put back into the mother. The availability of PGD is limited due to its high cost and a lack of centers that perform the procedure.
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