Benign essential blepharospasm (Benign essential blepharospasm) - Genes DRD5 and TOR1A.
The benign essential blepharospasm is a disorder characterized by abnormal blinking or eyelid spasms. This alteration is a type of dystonia, a group of movement disorders that involve muscle contractions, tremors and other involuntary movements. Benign essential blepharospasm is different from the temporal common eyelid spasm that can be caused by fatigue, stress or caffeine.
Signs and symptoms of this disease usually appear in mid to late adulthood and gradually worsen. Early symptoms of the disease include increased blink rate, dry eyes and irritation of the eyes, and is aggravated by wind, air pollution, sunlight and other irritants. These symptoms may begin in one eye but, ultimately, affects both eyes. As the disease progresses, spasms of the muscles around the eyes cause an involuntary nod. Affected individuals have increasingly difficult to keep your eyes open and can lead to severe impairment of vision. In more than half of all people affected, the symptoms affect other facial muscles and muscles in other areas of the body. When those affected also have oromandible dystonia, the combination of signs and symptoms is known as Meige syndrome.
Although benign essential blepharospasm probably results from a combination of genetic and environmental factors, the exact causes are unknown. Certain genetic changes are likely to increase the likelihood of developing the disease, and environmental factors can trigger signs and symptoms in people who are at risk. It is believed that this disease may be related to other forms of adult onset, including spasmodic torticollis and writer 's cramp. It is likely that variations in genes TOR1A DRD5 and increase the risk of developing benign essential blepharospasm.
The DRD5 gene, located on the short arm of chromosome 4 (4p16.1), encodes a known dopamine D5 receptor, located in the brain protein. This protein interacts with dopamine. Dopamine signaling has many critical functions in the brain, including the regulation of attention, mood, memory, learning and movement. We examined a possible link between a common variation in the DRD5 gene and benign essential blepharospasm. Some research has suggested that polymorphism, a short segment repeated DNA known as allele 2, occurs most often in people with benign essential blepharospasm than in people without the disease. However, other studies have found no connection between this polymorphism and benign essential blepharospasm. It is working to clarify whether DRD5 variants in the gene are associated with this disease.
The TOR1A gene, also known as DYT1, located on the long arm of chromosome 9 (9q34), encodes a protein called torsion A. This protein is found in the space between the nuclear envelope and endoplasmic reticulum. Although little about the role of Torsin A is known, it is likely to contribute to process and transport other proteins. Torsin A can also participate in the movement of the membranes associated with the nuclear envelope and endoplasmic reticulum. Torsin A is active in many tissues of the body, and is particularly important for the normal function of nerve cells in the brain. It has examined the possible relationship between changes in gene TOR1A and various forms of dystonia in adults, including benign essential blepharospasm. Some research has suggested that certain polymorphisms increase the risk of developing benign essential blepharospasm. However, other studies have found no relationship between changes in the TOR1A gene and the risk of developing the disease. It is working to clarify whether TOR1A gene variants are associated with benign essential blepharospasm and other adult dystonias.
Most cases are sporadic benign essential blepharospasm, which means that develop in people with no history of disease in your family. Less often, benign essential blepharospasm has been identified in some families. In some of these families, it seems to have an autosomal dominant pattern of inheritance, meaning that one copy of an altered gene in each cell is sufficient to express the disease. However, in these cases they have not identified the causative genes.
Tests performed in IVAMI: in IVAMI perform detection of mutations associated with benign essential blepharospasm, by complete PCR amplification of the exons of the DRD5 and TOR1A genes, respectively, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).