Which are the causes of Amelogenesis Imperfecta?

Amelogenesis Imperfecta (AI) is a rare genetic disorder that affects the development of tooth enamel, resulting in abnormal tooth formation. It is a hereditary condition that can be passed down from parents to their children. The exact causes of AI can vary depending on the specific type of the disorder, as there are several different subtypes with distinct genetic mutations involved.

1. Autosomal Dominant AI: This is the most common form of AI and is caused by mutations in the genes responsible for enamel formation. The affected gene can be inherited from either one of the parents. Mutations in genes such as ENAM, AMBN, and AMELX have been associated with autosomal dominant AI. These genes provide instructions for the production of proteins involved in enamel development.

2. Autosomal Recessive AI: This form of AI occurs when an individual inherits two copies of the mutated gene, one from each parent. Autosomal recessive AI is less common than the dominant form. Mutations in genes such as AMTN, KLK4, and FAM83H have been linked to autosomal recessive AI. These genes play a role in enamel matrix formation and mineralization.

3. X-Linked AI: This type of AI is caused by mutations in the AMELX gene, which is located on the X chromosome. As the X chromosome is inherited differently in males and females, X-linked AI predominantly affects males. Females can be carriers of the mutated gene without showing significant symptoms. The AMELX gene provides instructions for the production of amelogenin, a protein essential for enamel formation.

4. Hypoplastic AI: Hypoplastic AI is characterized by thin enamel that is insufficiently formed. It can be caused by mutations in genes involved in enamel matrix formation, such as AMBN and ENAM. These mutations disrupt the normal production and organization of enamel proteins, leading to enamel that is thin and prone to breakage.

5. Hypomaturation AI: Hypomaturation AI is characterized by enamel that is softer and less mineralized than normal. Mutations in genes such as KLK4 and FAM83H can lead to this type of AI. These genes are involved in the maturation and mineralization of enamel, and their mutations result in enamel that is more porous and prone to wear and discoloration.

It is important to note that while AI is primarily caused by genetic mutations, other factors such as environmental influences and certain medical conditions can also contribute to the severity and presentation of the disorder. Additionally, the specific genetic mutations associated with AI are still being researched, and there may be other genes involved that have not yet been identified.