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Bardet-Biedl syndrome

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Related terms
Background
Signs and symptoms
Diagnosis
Complications
Treatment
Integrative therapies
Prevention
Author information
Bibliography
Causes
Risk factors
Types of the disease

Related Terms
  • BBS, Biedl-Bardet syndrome, Laurence-Bardet-Biedl syndrome, Laurence-Moon syndrome (LMS), Laurence-Moon-Bardet-Biedl syndrome (LMBBS), Laurence-Moon-Biedl syndrome.

Background
  • Bardet-Biedl syndrome (BBS) is a rare genetic disorder that affects many areas of the body, primarily the eyes, hands, feet, genitals, and kidneys. In addition, people with BBS tend to be obese, have intellectual disabilities, and be at increased risk of diabetes, high blood pressure, and heart disease. In most people with BBS, visual impairment progresses to legal blindness by about age 16.
  • BBS overlaps with a condition known as Laurence-Moon syndrome. Controversy still exists as to whether these two syndromes are in fact distinct entities. Ultimately, BBS is distinguished from Laurence-Moon syndrome based on which genes are affected. However, one of the genetic mutations that cause BBS has also been found in individuals with Laurence-Moon syndrome, which illustrates the difficulty in distinguishing the two.
  • There are 14 types of BBS, each of which is caused by a different genetic mutation. These 14 genes are BBS1, BBS2, ARL6/BBS3, BBS4, BBS5, MKKS/BBS6, BBS7, TTC8/BBS8, B1/BBS9, C12ORF58/BBS10, TRIM/BBS11, C4ORF24/FLJ35630/BBS12, FLJ20345/MKS1, and CEP290. Most people with BBS have mutations in BBS1 or BBS10. These genes provide instructions for making several proteins, many of which are poorly understood.
  • BBS is usually inherited (passed down among family members) as an autosomal recessive trait. An individual inherits two copies of most genes, one from the mother and one from the father. To inherit an autosomal recessive disorder, an individual must inherit two defective copies of the mutated gene.
  • The prevalence of BBS in Europe and the United States ranges from one in 100,000 to one in 160,000. Research indicates that the prevalence of BBS is higher among people from Kuwait (about one in 13,500), where parents are frequently consanguineous (closely related). The prevalence in Newfoundland is estimated at about one in 17,500.
  • There is no known cure for BBS, but treatment focuses on the management of symptoms and prevention of complications.

Signs and symptoms
  • Cognitive function: A significant number of people with Bardet-Biedl syndrome (BBS) have learning and intellectual disabilities. These are typically not severe and may be associated with vision loss, which may impair an individual's ability to read and learn.
  • Eyes: People with BBS tend to have eye problems that worsen with time. The cells in the eyes that receive light (rods and cones) gradually deteriorate, which eventually leads to blindness. Most children with BBS lose the ability to see at night by age eight. Many become legally blind by age 16. Other eye problems may include nystagmus (involuntary eye movements), strabismus (crossed eyes), myopia (nearsightedness), cataract (clouding of the eye lens), and glaucoma (increased pressure in the eyes).
  • Face: People with BBS may have a distinctive facial appearance that includes a large, broad head, narrow temples, large ears, a thin upper lip, a small downturned mouth, and balding in the front of the hairline in males. The two sides of the face may not be symmetrical.
  • Genitals: In males with BBS, the penis and testes tend to be small and underdeveloped. Females may have structural abnormalities with the urinary system and genitals, such as problems with the Fallopian tubes, uterus, and ovaries. While there have been several reports of females with BBS bearing children, there have been only about two reports of males with BBS fathering children. It is unknown whether this is because of decreased male fertility in males with BBS.
  • Hands and feet: About 60-70% of people with BBS have an extra finger near the little finger or an extra toe near the little toe. Other symptoms that affect the hands and feet include short fingers and toes, fused fingers and toes, abnormal curvature of the little finger, and an abnormal gap between the first and second toes. These abnormalities may limit fine motor skills.
  • Kidneys: Many people with BBS have problems with the structure of the urinary system and kidneys. The ability to urinate may be affected by these structural abnormalities. Kidney problems can become severe and lead to life-threatening complications, such as kidney failure.
  • Obesity: People with BBS tend to have truncal or abdominal obesity (increased fatty tissue in the center or trunk of the body). Infants with BBS may have a normal birthweight but rapidly gain weight during the first year of life. Many people with BBS struggle with weight issues throughout their lives.
  • Other: Other problems associated with BBS include diabetes, high blood pressure, heart disease, impaired speech, poor coordination, abnormal gait, hearing loss, and psychological problems, including depression, anxiety, bipolar disorder, and obsessive-compulsive disorder.

Diagnosis
  • General: Diagnosis of Bardet-Biedl syndrome (BBS) may be delayed because of the slow and variable appearance of signs and symptoms. The primary features of BBS include progressive vision loss, extra fingers and toes, learning disability, underdeveloped or abnormal genitalia, abdominal obesity, and kidney problems. Secondary features include speech impairment, short or fused fingers or toes, developmental delays, increased hunger or thirst, liver problems, heart problems, dental problems, poor coordination, overdeveloped muscles in the lower body, and eye problems, such as involuntary eye movements, crossed eyes, nearsightedness, cataracts, or glaucoma.
  • Physical exam: A thorough physical exam and family history should be conducted. Patient interview questions should focus on eating and drinking habits, the pattern of weight gain, behavior, and the achievement of developmental milestones. A clinician should examine the hands and feet for extra fingers and toes and other abnormalities, the external genitals for abnormalities, the lower body muscles for overdevelopment, and the mouth for dental problems. Height and weight should be assessed to determine growth percentiles, and gait and coordination should be assessed using a standard neurological exam.
  • Eye exam: A thorough eye exam may identify nystagmus (involuntary eye movements),strabismus (crossing of the eyes),cataract (clouding of the lens of the eye), and glaucoma (increased pressure in the eye). A special test called an electroretinogram can help identify problems with the rod and cone cells of the retina.
  • Hearing test: A hearing test, called an audiogram, may help diagnose BBS. During an audiogram, the patient wears headphones and is exposed to various sounds of different pitches and frequencies. The patient is asked to identify when each sound is heard. The audiologist may also use speech to evaluate the patient's hearing ability.
  • Fasting blood glucose test: Fasting blood glucose testing can check for the presence of diabetes. This test measures blood glucose levels after the patient has fasted for 12-14 hours. The individual may drink water during this time but must avoid any other beverage. Individuals with diabetes may be asked to delay taking their diabetes medication or insulin dose until the test is completed. This test can be used to diagnose diabetes or prediabetes. The fasting plasma glucose (FPG) test is preferred for diagnosing diabetes because of its convenience. The FPG test is most reliable when done on an empty stomach in the morning, so that the presence of food and natural biorhythms do not cause fluctuations in blood sugar levels. If the fasting glucose level is 100-125 milligrams per deciliter, the individual has a form of prediabetes called impaired fasting glucose (IFG), meaning that the individual is more likely to develop type 2 diabetes but does not have the condition yet. A fasting glucose level of 126 milligrams per deciliter or above, confirmed by repeating the test on another day, means that the individual has diabetes.
  • Oral glucose tolerance test: An oral glucose tolerance test may also be used to diagnose diabetes in an individual with BBS. During an oral glucose tolerance test, a high-glucose drink is given to the individual. Blood samples are checked at regular intervals for two hours to determine how rapidly glucose is cleared from the blood. Glucose tolerance tests are used when the results of the fasting blood glucose test are borderline. They are also used to diagnose gestational diabetes (diabetes in pregnancy). This test can be used to diagnose diabetes or prediabetes.
  • Hemoglobin A1c: The hemoglobin A1c test is used to assess blood glucose control in individuals with diabetes. This test may be useful in some individuals with BBS who are prone to developing diabetes. Hemoglobin A1c, also known as glycated hemoglobin or glycosylated hemoglobin, analyzes a sample of blood to indicate an individual's average blood sugar control over the last 2-3 months. Glucose (sugar) in the bloodstream can become attached to the hemoglobin, the part of the cell that carries oxygen, in red blood cells. This process is called glycosylation. Once the sugar is attached, it remains there for the life of the red blood cell, about 120 days. The more sugar that attaches to red blood cells, the higher the level of blood sugar. The hemoglobin A1c test measures the amount of sugar adhering to the hemoglobin in the red blood cells. A1c is formed when glucose in the blood binds irreversibly to hemoglobin to form a stable glycated hemoglobin complex. A1c values are not subject to the fluctuations seen with daily blood glucose monitoring.
  • Kidney ultrasound: An ultrasound, which uses sound waves to create an image of internal organs, can be used to assess the structure and function of the kidneys. Structural abnormalities that may be present in BBS include the presence of fibrous tissue.
  • Echocardiogram: An echocardiogram is a special test that uses sound waves to create a moving image of the heart. This test can be used to assess the structure and function of the heart.
  • Fetal ultrasound: Although ultrasound cannot directly diagnose BBS in a developing fetus, it may help identify distinctive characteristics, such as extra fingers and toes.
  • Genetic testing: If BBS is suspected, a genetic test may be performed to confirm a diagnosis. A sample of the patient's blood is taken and analyzed to detect the presence of the mutated gene. If this gene is detected, a positive diagnosis can be made.
  • Prenatal DNA testing: If there is a family history of BBS, prenatal testing may be performed to determine whether the fetus has the disorder. Amniocentesis and chorionic villus sampling (CVS) can diagnose BBS. However, because there are risks associated with these tests, patients should discuss the potential health benefits and risks with a medical professional.
  • During amniocentesis, a long, thin needle is inserted through the abdominal wall and into the amniotic cavity, the sac surrounding the fetus within the uterus, and a small amount of fluid is removed. Cells in the fluid are then analyzed for normal and abnormal chromosomes. This test is usually performed between 14 and 20 weeks of pregnancy. At some facilities, it can be performed as early as at 11 weeks. The risk of miscarriage is about one in 200-400. Some patients may experience minor complications, such as cramping, leaking fluid, or irritation where the needle was inserted.
  • During chorionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the placenta between the ninth and 14th week of pregnancy. CVS may be performed through the cervix or through the abdomen. The cells in the tissue sample are then analyzed for the presence of the mutated gene. Miscarriage occurs in about 0.5-1% of women who undergo this procedure.

Complications
  • Diabetes: Individuals with Bardet-Biedl syndrome (BBS) are at increased risk of developing diabetes. This may be because of the presence of obesity, which also increases diabetes risk, or specific genetic defects responsible for BBS. With diabetes, the body cannot properly break down and use sugar for energy. Either the pancreas does not produce enough insulin, which is necessary to absorb dietary sugar and carbohydrates, or the body is not able to utilize insulin properly. This causes an increase of glucose (sugar) in the blood, which can cause damage to the heart, blood vessels, kidneys, eyes, and nerves. In addition, the cells of the body do not get adequate energy.
  • Complications of diabetes are divided into two major categories: macrovascular and microvascular. Macrovascular (large blood vessel) complications affect the heart. Microvascular (small blood vessel) complications affect the small blood vessels, especially in the eyes, kidneys, and nerves. Macrovascular complications can lead to heart disease and stroke. Microvascular complications can lead to vision problems, blindness, kidney failure, and nerve damage.
  • Heart disease: Individuals with BBS may develop heart disease caused by obesity, diabetes, and high blood cholesterol levels. They are also susceptible to atherosclerosis, the accumulation of cholesterol-laden plaques in arterial walls. Plaque accumulation causes a narrowing and a loss of elasticity of the arteries, which is sometimes referred to as hardening of the arteries.
  • Kidney disease: Kidney problems may range from mild to severe and can be life-threatening if not assessed and treated appropriately. These may include protein in the urine and glomerulonephritis, which is caused by inflammation of the kidney structures that help to filter out waste and fluids.

Treatment
  • General: There is no cure for Bardet-Biedl syndrome (BBS). Treatment focuses on reducing symptoms and preventing complications.
  • Education: Patients with BBS must have access to education tailored to their specific strengths and weaknesses. According to the Individuals with Disabilities Education Act, all children with disabilities must receive free and appropriate education. According to this law, staff members of the child's school must consult with the child's parents or caregivers to develop an individualized education plan. The school faculty should document the child's progress in order to ensure that the child's needs are being met.
  • Educational programs vary among patients. In general, most experts believe that children with disabilities should be educated alongside their nondisabled peers. The concept is that nondisabled students will help the disabled student learn appropriate behavioral, social, and language skills. For this reason, some children with BBS are educated in mainstream classrooms. Some children with BBS attend public schools but take special education classes, while others attend specialized schools for children with disabilities.
  • Speech-language therapy: Some children with BBS may benefit from speech-language therapy because they often develop communication skills at a slower-than-normal rate. During speech-language therapy, a qualified speech-language professional (SLP) works with the patient on a one-to-one basis, in a small group, or in a classroom. This therapy helps the patient improve speech, language, and communication skills. Programs are tailored to the patient's individual needs.
  • Speech pathologists use a variety of exercises to improve the patient's communication skills. Exercises typically begin at a low level and become more complex as therapy continues. For instance, the therapist may ask the patient to name objects, tell stories, or explain the purpose of an object.
  • Visual assistance: Eyeglasses may improve vision in people with BBS who are nearsighted. Because almost all people with BBS progressively lose vision, they should be instructed in the use of Braille, adaptive equipment, mobility aids, and special computing skills early in life.
  • Hearing aids: People with BBS who experience hearing loss may benefit from hearing aids. These battery-operated devices are available in three basic styles: behind the ear, in the ear, and in the ear canal. Patients should talk to their healthcare providers to determine the type of hearing aid that is best for them. A behind-the-ear device is used for mild-to-profound hearing loss. The device is worn behind the ear and is attached to a plastic ear mold inside the outer ear. In-the-ear hearing aids are worn inside the outer ear and are used for mild-to-severe hearing loss. Canal hearing aids are smaller aids that fit inside the patient's auditory canal. They are used for mild-to-moderately severe hearing loss. Some patients with severe hearing loss may benefit from cochlear implants. These electronic devices are surgically implanted in the cochlea (inner ear). Unlike a hearing aid, which amplifies sound, a cochlear implant makes up for damaged parts of the inner ear.
  • Diet: Consuming a healthful and appropriate diet is essential for people with BBS. Proper diet can help these individuals reduce the risks of obesity, heart disease, and diabetes. The progression of diabetes may be slowed by consuming a diet low in sugars and high in vegetables, whole grains, and lean protein. In fact, diet and exercise are often the first line of treatment for diabetes. An ideal diet for an individual with diabetes can be planned with a registered dietitian or certified diabetes educator.
  • Physical activity: People with BBS should follow a regular schedule of physical activity that is planned under the supervision of a qualified healthcare provider such as a physician. Exercise not only reduces obesity but also helps with the control of blood sugar levels.
  • Oral diabetes medications: A number of different drugs can be taken by mouth to treat diabetes. Some of these drugs can be combined into a single pill, which may be more effective and convenient than taking multiple drugs. Sulfonylureas, such as chlorpropamide (Diabinese®), glipizide (Glucotrol®), glyburide (Micronase®, Glynase®, DiaBeta®), and glimepiride (Amaryl®), work by stimulating the cells of the pancreas to release more insulin. These drugs are taken once or twice daily by mouth before meals. Side effects may include an unsafe drop in blood sugar.
  • Meglitinides, such as repaglinide (Prandin®) and nateglinide (Starlix®), also stimulate the cells of the pancreas to release more insulin. These drugs are taken by mouth before each meal and may also cause an unsafe drop in blood sugar.
  • Metformin (Glucophage®) is a biguanide drug that decreases the amount of blood sugar released by the liver and stimulates cells in the muscles to take up blood sugar. Metformin is usually taken twice daily and may cause stomach discomfort.
  • Thiazolidinediones, such as rosiglitazone (Avandia®) and pioglitazone (Actos®), are drugs that help insulin work better in the muscle and fat cells and cause the liver to release less glucose. These drugs may be associated with heart failure, and their use should be thoroughly discussed with a qualified healthcare provider, including a pharmacist.
  • DPP-4 inhibitors, such as sitagliptin (Januvia®), are drugs that improve levels of blood sugar by decreasing the action of an enzyme that breaks down GLP-1, a substance that naturally lowers blood sugar levels.
  • Alpha-glucosidase inhibitors, such as acarbose (Precose®) and miglitol (Glyset®), block the breakdown of certain carbohydrates so that they are excreted from the body. Side effects include intestinal gas and diarrhea.
  • Injected diabetes medications: Other diabetes drugs can be taken by injection into the muscle. Pramlintide (Symlin®) is the synthetic form of a hormone that naturally occurs in the human body. Taken with meals, pramlintide helps maintain normal levels of blood sugar but may cause nausea.
  • Exenatide (Byetta®) is a synthetic form of exendin-4, a substance that naturally occurs in the body. This substance helps increase insulin secretion from the pancreas. It may cause nausea, but this side effect usually decreases with continued usage.
  • Depending on the type and severity of diabetes, insulin may be injected subcutaneously (just below the skin). Insulin allows the body to convert the glucose (sugar) in the blood into energy. Many different types of insulin are available, and a treatment strategy can be tailored to individual patient needs. Use of insulin therapy should be thoroughly discussed with a qualified healthcare provider and a certified diabetes educator.
  • Cholesterol-lowering drugs: Drugs that lower cholesterol and triglyceride levels may be appropriate in some people with BBS. HMG-CoA reductase inhibitors, or statins, such as atorvastatin (Lipitor®) or lovastatin (Mevacor®), effectively lower levels of low-density lipoprotein (LDL, or "bad") cholesterol and triglycerides. High-dose nicotinic acid (niacin) can also reduce cholesterol levels. Side effects of statins may include headache, nausea, vomiting, constipation, diarrhea, rash, weakness, and muscle pain. Rhabdomyolysis is a very rare but potentially life-threatening side effect of statins that is characterized by severe muscle damage. Statins are contraindicated in pregnancy and breastfeeding.
  • Antibiotics: Some people with BBS may be given antibiotics prior to surgical or dental procedures to protect against infections.
  • Dialysis: If the kidneys begin to fail, patients can undergo dialysis to cleanse the body of toxic substances. With hemodialysis, a patient's blood is circulated into an external filter and cleansed. The filtered blood is then returned to the body. With peritoneal dialysis, a fluid containing dextrose is introduced into the abdomen through a tube. This solution absorbs the wastes in the body and is then removed.
  • Transplantation: Some patients who experience kidney failure may undergo kidney transplantation. Transplantation is associated with complications, including infection and the possibility of organ rejection. To reduce the risk of rejection, patients may need to take immunosuppressant drugs. In people with BBS, immunosuppressant drugs may worsen obesity.
  • Surgery: People with BBS may have surgery to remove extra fingers and toes. Dental extraction may be necessary if crowding of the teeth is a problem. In addition, surgery may be used to correct problems with the genitourinary system.

Integrative therapies
  • Currently, there is a lack of scientific data on the use of integrative therapies for the treatment or prevention of Bardet-Biedl syndrome (BBS).

Prevention
  • General: Because Bardet-Biedl syndrome (BBS) is an inherited condition, there is currently no known way to prevent the disease. However, a number of options are available for patients with family histories of BBS.
  • Genetic testing and counseling: Individuals who have BBS may meet with a genetic counselor to discuss the risks of having children with the disease. Individuals with a family history of BBS may meet with genetic counselors to determine whether they carry a defective gene. Carriers can be determined through detailed family histories or genetic testing.
  • Known carriers of BBS may undergo genetic counseling before they conceive a child. Genetic counselors can explain the options and the associated risks of various tests, including preimplantation genetic diagnosis (PGD), amniocentesis, and chorionic villus sampling (CVS).
  • Preimplantation genetic diagnosis (PGD) may be used with in vitro fertilization (IVF). In PGD, embryos are tested for the defective gene, and only the embryos that are not affected are selected for implantation. Because BBS can be detected in a fetus, parents may choose whether or not to continue the pregnancy. Genetic counselors may assist parents with these difficult decisions.

Author information
  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
  1. Beales PL, Elcioglu N, Woolf AS, et al. New criteria for improved diagnosis of Bardet-Biedl syndrome: results of a population survey. J. Med. Genet. 1999;36: 437-46.
  2. Cox GF, Hansen RM, Quinn N, et al. Retinal function in carriers of Bardet-Biedl syndrome. Arch. Ophthal. 2003;121: 804-10.
  3. Croft JB, Morrell D, Chase CL, et al. Obesity in heterozygous carriers of the gene for the Bardet-Biedl syndrome. Am. J. Med. Genet. 1995; 55: 12-5, 1995.
  4. David A, Bitoun P, Lacombe D, et al. Hydrometrocolpos and polydactyly: a common neonatal presentation of Bardet-Biedl and McKusick-Kaufman syndromes. J. Med. Genet. 1999;36: 599-603.
  5. Elbedour K, Zucker N, Zalzstein E, et al. Cardiac abnormalities in the Bardet-Biedl syndrome: echocardiographic studies of 22 patients. Am. J. Med. Genet. 1994;52: 164-9.
  6. Green JS, Parfrey PS, Harnett JD, et al. The cardinal manifestations of Bardet-Biedl syndrome, a form of Laurence-Moon-Biedl syndrome. N. Engl. J. Med. 1989;321: 1002-9.
  7. Katsanis N, Beales PL, Woods MO, et al. Mutations in MKKS cause obesity, retinal dystrophy and renal malformations associated with Bardet-Biedl syndrome. Nature Genet. 2000;26: 67-70.
  8. LMBBS Society. .
  9. Moore SJ, Green JS, Fan Y, et al. Clinical and genetic epidemiology of Bardet-Biedl syndrome in Newfoundland: a 22-year prospective, population-based, cohort study. Am. J. Med. Genet. 2005;132A: 352-60.
  10. Mykytyn K, Braun T, Carmi R, et al. Identification of the gene that, when mutated, causes the human obesity syndrome BBS4. Nature Genet. 28: 188-91, 2001.
  11. Mykytyn K, Nishimura DY, Searby CC, et al. Identification of the gene (BBS1) most commonly involved in Bardet-Biedl syndrome, a complex human obesity syndrome. Nature Genet. 2002;31: 435-8.
  12. Natural Standard: The Authority on Integrative Medicine. .

Causes
  • Genetic mutations: Bardet-Biedl syndrome (BBS) is caused by one or more mutations or defects in the following genes: BBS1, BBS2, ARL6/BBS3, BBS4, BBS5, MKKS/BBS6, BBS7, TTC8/BBS8, B1/BBS9, C12ORF58/BBS10, TRIM/BBS11, C4ORF24/FLJ35630/BBS12, FLJ20345/MKS1, and CEP290. These genes provide instructions for making various proteins, many of which are poorly understood. The type of BBS depends on which genetic mutation is present. About 20-30% of individuals who have BBS do not have mutations in any of these genes, suggesting that additional but as yet unknown genes may be involved. In some cases, a mutation in the CCDC28B gene will alter the way a typical BBS genetic mutation is expressed. The CCDC28B gene provides instructions for making the coiled-coil domain-containing protein 28B, the function of which is poorly understood but which may play a role in the normal functioning of the retina or of the eye, heart, and limbs.
  • Autosomal recessive inheritance: BBS is usually inherited as an autosomal recessive trait, meaning that a person must inherit two copies of the defective gene (one from each parent) in order to have the disease. Individuals who inherit only one copy of the defective gene generally have no symptoms and are called "carriers," because they can pass the disorder on to their children.
  • If one parent is a carrier (has only one copy of the defective gene), then each child will have a 50% chance of inheriting one defective gene and also of being a carrier. If both parents are carriers, each child has a 25% chance of inheriting two defective genes, a 50% chance of inheriting only one defective gene, and a 25% chance of inheriting neither defective gene.
  • Random occurrence: It is not known whether BBS can occur in people with no family history of the disorder.

Risk factors
  • Because Bardet-Biedl syndrome (BBS) is inherited, the only known risk factor is a family history of the disorder.
  • Prevalence of BBS in Europe and America ranges from one in 100,000 to one in 160,000. Research indicates that the prevalence of BBS is higher among people from Kuwait, about one in 13,500, where parents are frequently consanguineous (closely related). Its prevalence in Newfoundland is estimated at about one in 17,500.

Types of the disease
  • General: Types of Bardet-Biedl syndrome (BBS) are distinguished by which gene is affected. Symptoms of the various types of BBS are similar except where otherwise indicated below.
  • Bardet-Biedl syndrome type 1: BBS type 1 is caused by a mutation of the BBS1 gene. This gene has been found to have widespread activity in the body, including in fetal tissues, testes, the retina, and adipose (fat) tissue. The BBS1 gene provides instructions for making the BBS1 protein, the function of which is currently poorly understood. People with BBS type 1 tend to be taller than their parents.
  • Bardet-Biedl syndrome type 2: BBS2 is caused by a mutation in the BBS2 gene. This gene has widespread activity in the body, including in the brain, kidney, adrenal gland, and thyroid gland. The BBS2 gene provides instructions for making the BBS2 protein, the function of which is currently poorly understood. People with BBS type 2 tend to be shorter than their parents.
  • Bardet-Biedl syndrome type 3: BBS3 is caused by a mutation of the BBS3 gene, which is also known as the ARL6 gene. The BBS3 gene provides instructions for making the ADP-ribosylation factor-like protein 6. This protein appears to help regulate various cell functions.
  • Bardet-Biedl syndrome type 4: BBS type 4 is caused by a mutation of the BBS4 gene. The BBS4 gene provides instructions for making the BBS4 protein, which may play a role in insulin resistance and therefore in the development of diabetes. People with BBS type 4 tend to be shorter than their parents.
  • Bardet-Biedl syndrome type 5: BBS type 5 is caused by a mutation of the BBS5 gene. The BBS5 gene provides instructions for making the BBS protein 5 isoform 2, which is involved in the generation of special cell structures called cilia and flagella.
  • Bardet-Biedl syndrome type 6: BBS type 6 is caused by a mutation of the BBS6 gene, which is also known as the MKKS gene. This gene is also mutated in a condition known as McKusick-Kaufman syndrome (MKKS). The BBS6 gene provides instructions for making the MKKS/BBS putative chaperonin protein, which has activity in the retina, brain, pancreas, and other organs and may be involved in the development of obesity.
  • Bardet-Biedl syndrome type 7: BBS type 7 is caused by a mutation of the BBS7 gene. This gene has activity in most of the tissues of the body. The BBS7 gene provides instructions for making the BBS7 protein, the function of which is currently poorly understood.
  • Bardet-Biedl syndrome type 8: BBS type 8 is caused by a mutation of the BBS8 gene, which is also known as the TTC8 gene. The BBS8 gene provides instructions for making the tetratricopeptide repeat protein 8, the function of which is currently poorly understood but which may be involved in the generation of special cell structures called cilia and flagella.
  • Bardet-Biedl syndrome type 9: BBS type 9 is caused by a mutation in the BBS9 gene, which is also known as the B1 gene. This gene has activity in many tissues of the body, including the adult heart, skeletal muscle, lungs, liver, kidneys, placenta, and brain. In addition, the BBS9 gene has activity in the fetal kidney, liver, and brain. The BBS9 gene provides instructions for making the parathyroid hormone-responsive B1 protein. The function of this protein is poorly understood, but it may be involved in the eye problems characteristic of BBS.
  • Bardet-Biedl syndrome type 10: BBS type 10 is caused by a mutation of the BBS10 gene, which is also known as the C12ORF58 gene. The BBS10 gene provides instructions for making the BBS10 protein, the function of which is currently poorly understood.
  • Bardet-Biedl syndrome type 11: BBS type 11 is caused by a mutation of the BBS11 gene, which is also known as the TRIM32 gene. The BBS11 gene provides instructions for making the tripartite motif protein 32, the function of which is currently poorly understood.
  • Bardet-Biedl syndrome type 12: BBS type 12 is caused by a mutation of the BBS12 gene, which is also known as the C4ORF24 or FLJ35630 gene. The BBS12 gene provides instructions for making the BBS12 protein. The function of this protein is poorly understood, but it may be involved with the ability of the eye to detect light.
  • Bardet-Biedl syndrome type 13: BBS type 13 is caused by a mutation of the MKS1 gene, which is also known as the FLJ20345 gene. This gene appears to have activity in the brain, liver, kidneys, and fingers. The MKS1 gene provides instructions for making the MKS1 protein. The function of this protein is poorly understood, but it may play a role in lung development.
  • Bardet-Biedl syndrome type 14: BBS type 14 is caused by a mutation of the CEP290 gene. This gene provides instructions for making the centrosomal protein, the function of which is currently poorly understood but which may be involved in the generation of special cell structures called cilia.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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