Which are the causes of Treacher Collins syndrome?

Treacher Collins syndrome, also known as mandibulofacial dysostosis, is a rare genetic disorder that affects the development of facial bones and tissues. It is named after the English surgeon Edward Treacher Collins, who first described the condition in 1900. This syndrome is characterized by a range of craniofacial abnormalities, primarily affecting the ears, eyes, cheekbones, and jaw.

Causes:

Treacher Collins syndrome is primarily caused by mutations in the TCOF1, POLR1C, or POLR1D genes. These genes provide instructions for making proteins that are essential for the normal development of facial structures during embryonic development. Mutations in these genes disrupt the production or functioning of these proteins, leading to the characteristic features of Treacher Collins syndrome.

The TCOF1 gene mutation is the most common cause of Treacher Collins syndrome, accounting for approximately 80% of cases. This gene provides instructions for making a protein called treacle, which plays a crucial role in the early development of facial bones and tissues. Mutations in the TCOF1 gene result in reduced levels or abnormal functioning of treacle, leading to the characteristic facial abnormalities seen in affected individuals.

Less commonly, mutations in the POLR1C or POLR1D genes can cause Treacher Collins syndrome. These genes are involved in the production of RNA polymerase I, which is essential for the synthesis of ribosomal RNA. Ribosomal RNA is a crucial component of ribosomes, the cellular structures responsible for protein synthesis. Mutations in POLR1C or POLR1D genes disrupt ribosomal RNA production, leading to impaired protein synthesis and abnormal development of facial structures.

Inheritance:

Treacher Collins syndrome is typically inherited in an autosomal dominant manner, which means that a person only needs to inherit one copy of the mutated gene from either parent to develop the condition. However, in some cases, the syndrome can also occur due to spontaneous mutations that are not inherited from either parent.

Genetic Testing:

Genetic testing can be performed to confirm a diagnosis of Treacher Collins syndrome. This involves analyzing the specific genes associated with the condition to identify any mutations or abnormalities. Genetic testing can also help determine the likelihood of passing the syndrome on to future generations.

Other Factors:

While Treacher Collins syndrome is primarily caused by genetic mutations, other factors can influence the severity and presentation of the condition. Environmental factors, such as exposure to certain medications or toxins during pregnancy, may contribute to the variability in symptoms observed among affected individuals. Additionally, genetic modifiers and other yet unknown factors may also play a role in the development of the syndrome.

Conclusion:

Treacher Collins syndrome is a genetic disorder primarily caused by mutations in the TCOF1, POLR1C, or POLR1D genes. These mutations disrupt the normal development of facial bones and tissues, leading to the characteristic craniofacial abnormalities seen in affected individuals. The syndrome is typically inherited in an autosomal dominant manner, but spontaneous mutations can also occur. Genetic testing can help confirm the diagnosis and provide information about the likelihood of passing the syndrome on to future generations. While genetic mutations are the primary cause, other factors such as environmental influences and genetic modifiers may contribute to the variability in symptoms observed among individuals with Treacher Collins syndrome.