Синдром Тричера-Коллинза влияет на развитие bone and other facial tissues. The signs and symptoms of this disorder can vary significantly, from almost imperceptible to severe. Most of the victims have undeveloped facial bones, in particular, cheekbones, and a very small jaw and chin (in newborns). Some people with the Tricer-Colins syndrome are born with a hole in the mouth, which is called a "wolf's mouth." In severe cases, undeveloped facial bones can limit the affected airways, causing potentially life-threatening diseases.
Often in people with this disease, the eyes are tilteddown, rare eyelashes, there is a defect of the lower eyelids, which is called coloboma. This causes additional ophthalmic disturbances, which can lead to loss of vision. In addition, small or unusually formed ears or their absence are possible. Hearing loss occurs in about half the cases. It is caused by the defects of three small ossicles of the middle ear that transmit sound, or the undeveloped ear canal. The presence of the syndrome of Tricer-Collins does not affect the intellect: as a rule, it is normal.
Mutations of which genes cause the Tricer-Collins syndrome?
The most common reason:mutations of the genes TCOF1, POLR1C or POLR1D. The gene mutation of TCOF1 is the cause of 81-93% of all cases. POLR1C and POLR1D - an additional 2% of cases. In persons without a specific mutation of one of the genes, the cause of the disease is unknown.
The genes TCOF1, POLR1C, and POLR1D play an important role inearly development of bones and other facial tissues. They are involved in the production of a molecule called ribosomal RNA (rRNA), a chemical cousin of DNA. Ribosomal RNA helps to assemble blocks of proteins (amino acids) into new proteins that are necessary for the normal functioning and survival of cells. Mutations of the TCOF1, POLR1C, or POLR1D genes reduce the production of rRNA. Researchers believe that reducing the amount of rRNA can lead to the self-destruction of certain cells involved in the development of facial bones and tissues. Abnormal cell death can lead to certain problems with facial development in people with the Tricer-Collins syndrome.
How is the Tricer-Collins syndrome inherited?
If the disease occurs due to the mutation of TCOF1 genesor POLR1D, it is believed that this is an autosomal dominant disease. About 60% of cases appear as a result of new mutations in the gene and are in people without a history in the family. In other cases, the syndrome is inherited through a modified gene from the parents.
When the disease is caused by mutations of the POLR1C gene,it is believed that this is an autosomal recessive type of inheritance. Parents of an individual with an autosomal recessive disease have one copy of the mutated genes, but they usually do not show signs and symptoms of the disease.
Treatment of the syndrome
Treatment depends on the severity of the condition, but may include:
- genetic counseling - for an individual or for the whole family, depending on whether the disease is hereditary or not;
- hearing aids - in the case of conductive hearing loss;
- dental treatment, including orthodontic, aimed at correcting an incorrect occlusion;
- logopedic exercises to improve communication skills. Defectologists also work with people who have problems with swallowing food or drinks;
- surgical methods that will help improve the appearance and quality of life.
