Introduction
Bardet Biedl syndrome is a genetic condition that presents with various symptoms, including impaired speech, delayed development of motor skills such as standing and walking, behavioral issues such as emotional immaturity and inappropriate outbursts, and clumsiness or poor coordination. Nearly 20 genes have been mutated that cause Bardet Biedl syndrome. The diagnosis is challenging because of varying symptoms, and there are no specific treatments for this condition.
What Is Bardet Biedl Syndrome (BBS)?
Bardet Biedl syndrome is a condition characterized by several symptoms that are highly variable. These symptoms include degeneration of the retina, obesity (especially fat deposition along the abdomen), impaired kidney function, extra fingers or toes (polydactyly), intellectual impairment, etc. Generally, the functioning of the kidneys, eyes, and genitals is impaired. Vision loss is one of the main features of this condition, and it has been reported in most cases. During this condition, the retina (light-sensing tissue present at the back of the eye) starts deteriorating. Eventually, it leads to vision problems like night blindness, peripheral vision, blind spots, etc.
What Are the Other Names of Bardet Biedl Syndrome?
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Earlier, this condition was known as Laurence-Moon-Bardet syndrome.
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BBS.
What Causes Bardet Biedl Syndrome?
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Bardet Biedl syndrome occurs due to mutation in twenty different genes. Mutation refers to a change in the nucleic acid sequence in the gene. Some of the genes responsible for getting mutated and leading to Barder Biedl syndrome are BBS1, BBS2, ARL6, BBS4, BBS5, MKKS, BBS7, TTC8, BBS9, BBS10, TRIM32, BBS12, MKS1, CEP290, WDPCP, SDCCAG8, LZTFL1, BBIP1, IFT72, and C8ORF3.
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Even though many genes have already been linked to BBS, gene mutations have yet to be discovered in 20 % to 30 % of BBS patients. Moreover, there is no direct link between various mutated genes and the severity of the condition.
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Specific symptoms of Bardet Biedl syndrome occur due to ciliary dysfunction (dysfunction of microscopic organelles known as cilia). These findings are the characteristic cone-rod dystrophy (an eye disorder) and kidney abnormalities, less prevalent anosmia (inability to smell), hearing loss, and situs invertus. Situs invertus refers to the arrangement of the internal organs as a mirror image of normal anatomy.
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Mutations in the BBS1 gene cause around a quarter of all instances of Bardet-Biedl syndrome. Mutations in the BBS10 gene are responsible for another 20 % of cases. Each of the other genes is responsible for only a small percentage of all cases of this disease.
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The cause of Bardet-Biedl syndrome is unknown in around 25 % of the cases.
Is Bardet Biedl Syndrome a Common Condition?
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Bardet Biedl syndrome is not a very common condition, and it affects both men and women equally.
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Bardet Biedl syndrome is classified as a "rare disease,” affecting about 1 in 250,000 persons globally.
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In most of North America and Europe, the incidence rate is one in 1,00,000 of the population.
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The condition is more prevalent in Newfoundland is 1 in 17,500, and in Sweden. It is 1 in 160,000 of the population.
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The condition is prevalent amongst the Bedouin population in Kuwait, affecting 1 in every 13,500 people.
Is Bardet Biedl Syndrome an Inherited Condition?
Yes, Bardet Biedl syndrome is an inherited condition, and an inherited condition refers to a medical condition or disease genetically transferred from parents to their children. Bardet Biedl syndrome is usually inherited in an autosomal recessive pattern, meaning both BBS gene copies in each cell should have mutations. The parents of a person with an autosomal recessive disorder each have one copy of the mutated gene, but they usually do not display any signs or symptoms of the disease.
What Are the Symptoms of Bardet Biedl Syndrome?
The symptoms of Bardet Biedl syndrome are numerous and variable, and they vary even amongst people of the same family. However, the primary characteristic symptoms are:
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Vision problems occur due to retinal abnormalities.
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Obesity or truncal obesity is evident from the first year of life.
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Extra fingers or toes.
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Hypogonadism (failure of testes in men and ovaries in women to function correctly).
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Kidney dysfunction.
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Intellectual impairment or learning disabilities.
Secondary characteristics include:
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Developmental delay.
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Altered behaviors.
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Neurological problems.
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High blood pressure.
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Speech problems.
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Small teeth and small mandible (lower jaw).
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Anosmia (loss of sense of smell).
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Flat and wide feet.
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Thyroid dysfunctions.
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Short stature.
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Short and curved toes and fingers.
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Heart and blood vessel problems.
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Arrhythmias (irregular heartbeat).
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Liver problems.
How Is Bardet Biedl Syndrome Diagnosed?
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The diagnosis of Bardet Biedl syndrome is made primarily by evaluating the physical and clinical signs and symptoms.
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Because Bardet Biedl syndrome is associated with varying expression of the classic symptoms and diagnosis is reliant on clinical observations, some individuals may not have a definitive diagnosis for many years.
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Consultation with an ophthalmologist may be required for the diagnosis of retinal disease. In addition, an examination, including an electroretinogram (ERG), may be done. The ERG is a test that evaluates the retina's electrical response to light stimulation.
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For certain people, genetic testing may assist in confirming the diagnosis.
How Is Bardet Biedl Syndrome Treated?
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The principal therapeutic goal for people with Bardet Biedl syndrome is to address the specific symptoms that each person is experiencing.
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Currently, there is no specific treatment for Bardet Biedl syndrome. However, several therapies, including physical, occupational, speech, and vision services, help give symptomatic relief.
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Stem cell therapy involves delivering new cells that do not have the mutated BBS gene and can grow and replace damaged cells in the body.
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Gene therapy involves replacing the defective gene inside existing cells instead of replacing the cell.
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In suppressor therapy, rather than altering DNA (deoxyribonucleic acid) in new cells or existing cells, suppressor therapy aims to improve the function of those cells by inhibiting the activity of other genes or cellular pathways.
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Extra digits, genitourinary abnormalities, and congenital heart problems are among the physical abnormalities associated with Barder Biedl syndrome that can be corrected with surgery. However, kidney transplantation may be necessary if a severe renal disease develops later in life.
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Obesity is a prevalent component of Bardet Biedl syndrome. Thus it's especially crucial to address it. A healthy lifestyle that includes athletic interests can have a significant impact. Diet and exercise regimes are also strongly advised. Dietary management can help you avoid weight-related problems later in life.
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Individuals with Bardet Biedl syndrome should have regular ophthalmologic exams and maintain track of their prescription lenses as they change.
Conclusion
Bardet Biedl syndrome is a condition characterized by several symptoms that are numerous and variable. Blindness, obesity, hypertension, and diabetes mellitus are symptoms of Bardet-Biedl syndrome, which has a poor prognosis. In addition, renal failure is a common and deadly condition. There is a significant reduction in survival due to all these associated symptoms. However, with proper therapy, several problems can be resolved.
