Bardet-Biedl syndrome is a rare, inherited disorder that causes a number of abnormalities in the way certain parts of the body function, including a person’s vision. Named after Georges Bardet and Arthur Biedl, the physicians who independently described the disorder in the 1920s, vision loss associated with the syndrome takes the form of retinal dystrophy, with central vision loss often experienced first and with a gradual deterioration of vision occurring through adolescence into adulthood. It is not unusual for affected individuals to be legally blind by early adulthood. According to the National Institutes of Health, the disease affects somewhere between 1 in 140,000 to 1 in 160,000 individuals but is more common in Newfoundland and Labrador, which is genetically isolated. The prevalence of the syndrome in that province is approximately 1 in 17,000.
Several genes are linked to Bardet-Biedl syndrome, and they all play roles in the management and structure of cilia, which are the slender protrusions that extend from the main body of many cells (“cilium,” the singular for “cilia,” is Latin for “eyelash”). Since these structures—or “organelles”—play an important role in the transmission of chemical signals that allow cells to communicate, including the signals involved in cell growth and sensory perception, mutations that impact cilia can lead to a number of irregularities, in sight and elsewhere.
Beyond vision loss, other symptoms associated with the disease include:
- Obesity, usually more pronounced in the area of the torso—also called “truncal obesity.”
- Extra fingers and/or toes (a congenital disorder called “polydactyly”), or minor abnormalities of the hands and feet such as slight webbing or extra skin between the fingers and toes.
- Lack of or decreased secondary sex characteristics—a phenomenon termed “hypogonadism.”
- Developmental delay.
- Kidney problems.
Since the disease is complex, and since the expression of its associated genes varies between patients, diagnosis can be difficult. Physicians will often use a set of diagnostic criteria that include a range of symptoms, including many of those listed above. The disease does have genetic markers, however, and is inherited from one’s parents; as a result, while genetic testing is by no means definitive, it can be an essential component of a diagnosis, helping to determine the gene or genes that have been mutated, as well as the hereditary factors that are involved.
Existing Treatment and Standard of Care
Currently, there is no treatment or cure for Bardet-Biedl syndrome (BBS). There are, however, a number of clinical trials testing experimental treatments for inherited forms of blindness. One such treatment has already reached the market in the United States. Called Luxturna, it has the potential to halt vision loss and even restore some sight in individuals with a biallelic mutation of their RPE65 gene (manifesting as either retinitis pigmentosa or Leber congenital amaurosis).
Though Bardet-Biedl syndrome entails a more complex set of symptoms and results from a different set of mutations, none of which are RPE65, the approval and emergence of Luxturna shows that similar gene therapies could be used to treat other genetic disorders in the future. Importantly, this development has paved the way for the future of gene therapies by charting the path from the early, basic research phase right through to the approved treatment stage. This has already led to policy changes that will make future gene therapy research faster, and the approval stages much more efficient.
Thanks to support from the Bardet-Beidl Family Association, FBC is very proud to be supporting gene therapy research that aims to generate a new treatment for BBS that is caused by a mutation in the BBS10 gene.
Clinical trials are essential to the scientific process of developing new treatments: they test the viability and safety of experimental drugs and techniques, called “interventions,” on human beings. While there is no guarantee that enrolling in a clinical trial will provide any medical benefit, some patients do experience positive results after receiving an experimental therapy.
The website clinicaltrials.gov is a centralized database of clinical trials that are offered globally. But as the disclaimer on the site’s home page states, there is no guarantee that a listed trial has been evaluated or approved—the National Institutes of Health runs the site but does not vet its content. This means that there could be bogus or dangerous trials listed that are preying on patients. It is essential that you discuss a clinical trial with your ophthalmologist before enrolling, and that you pay close attention to enrollment criteria.
If you are interested in exploring what is available on the site you can click on the button below, which will take you to clinicaltrials.gov and initiate a search for trials relevant for patients living with Bardet-Beidl Syndrome.
For individuals living with an inherited retinal disease (a disease caused by a genetic mutation), such as Bardet-Beidl Syndrome, participation in a clinical trial could be a logical next-step (for a description of clinical trials, see above). But in Canada there is no centralized, guided mechanism for enrolling in a trial; with this in mind, Fighting Blindness Canada has developed a secure medical database of Canadian patients living with inherited retinal diseases. We call it the Patient Registry.
By enrolling in the Patient Registry, your information will become a part of this essential Canadian database that can be used to help connect you to a relevant clinical trial. The availability of relevant trials depends on a number of factors, so this tool provides no guarantees, but signing onto it will put you in a position to be connected to something appropriate. It is also a way of standing up and being counted: the more individuals enrolled in the Patient Registry, the better our chances of showing policymakers that there is a significant need for new treatments for inherited retinal diseases. The Patient Registry also helps to drive more sight-saving research!
You can begin the process of enrolling in the Patient Registry by clicking the button below.
Research Developments and Health Policy
Fighting Blindness Canada is committed to advancing the most promising sight-saving research, and has invested over $40 million into cutting-edge science and education since the organization was founded. Recognizing that science is tied to policy frameworks, FBC is also actively involved in health policy activities across Canada.
Many research groups are working to develop treatments and cures for Bardet-Beidl Syndrome. Experimental treatments can be divided into three broad categories:
- Protective Therapies
- Corrective Therapies
- Sight-Restoring Therapies
Protective therapies aim to stop (or at least slow) the damage caused by genetic mutations. Often protective therapies are not specific to one mutation, but may benefit people with different genetic forms of Bardet-Beidl Syndrome. These include treatments to stop the process of photoreceptor death (apoptosis), as well as cell-derived therapies that aim to help photoreceptors survive.
Some protective therapies are being developed to specifically to prevent the death of cone photoreceptor cells and thus, prevent the loss of central vision.
Corrective therapies aim to reverse the underlying genetic mutations that cause vision loss. If these therapies are successful they might prevent a person who is treated when first diagnosed, from ever developing vision loss. Corrective therapies might also help slow the disease in people whose vision has already been affected, especially in the earlier stages. The corrective therapies being developed now are specific to certain genetic forms of Bardet-Beidl Syndrome. Gene therapies, which replace a non-functioning gene, are one type of corrective therapy. Clinical trials of gene therapies for several kinds of inherited retinal diseases are underway, and the results so far are encouraging.
Sight-restoring therapies are also a growing area of research success. These therapies are intended for people who have already lost all, or much, of their vision. Stem cell therapies aim to replace the retina’s lost photoreceptors. There are promising early results with stem cell trials involving other retinal degenerative diseases, such as age-related macular degeneration. Retinal prosthetics, such as the Argus II or “Bionic Eye,” use computer technology to generate vision. Fighting Blindness Canada helped to support the first Canadian trial of the Argus II and continues to work closely with health policy experts across Canada to ensure that patients who could benefit from the Argus II device have access to this innovative treatment. Drug and gene therapies are also being developed that may give non-photoreceptor nerve cells in the retina the capacity to sense light.
Thanks to our generous donors, we are funding ground-breaking research in these areas. Click on the button below to review the full list of FBC-funded projects:
At the bottom of this webpage, you will find an updating list of stories that detail new research and health policy developments relevant for individuals affected by Bardet-Beidl Syndrome.
Fighting Blindness Canada has developed additional resources that can be helpful in plotting an optimal path through vision care. Below awe share links to our must-read resources, where you will find information on genetic testing, clinical trials, stem cell research, and more as well as View Point (FBC’s virtual education series).
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Updated on July 18, 2018.
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