BBS is a rare genetic disorder affecting many organ systems. Setting up a multidisciplinary care team early can help reduce chances of additional complications.
Bardet-Biedl syndrome (BBS) is a rare genetic disorder affecting approximately
- eyes
- kidneys
- reproductive system
- brain
- heart
Other complications can occur as well, such as abnormal weight distribution or the development of extra fingers or toes.
BBS is caused by a genetic alteration that affects the way cilia function within the body. Cilia are tiny, hair-like structures found throughout the body that play roles in sensory processing and signaling.
When these don’t work like they’re supposed to, it can lead to a variety of complications, such as symptoms in a person with BBS.
Read on to learn more about BBS, including symptoms, life expectancy, and treatment options.
Symptoms of BBS are typically present at birth or develop within the first year of life. Although symptoms can vary from person to person, the condition is typically defined by six key features.
Polydactyly
Polydactyly refers to the presence of extra fingers or toes at birth. It’s one of the earliest signs of BBS. About 70% of people with BBS are born polydactyl.
An extra toe digit to the little toe is the most common form of polydactyly in BBS, but people may also be born with an extra finger next to the pinky.
In about
Other changes to the anatomy of the digits may also be seen. Some people with BBS may have syndactyly, or webbing between the toes or fingers (usually between the second and third toes). Other people may have abnormally short toes or short, widened feet.
Obesity
Obesity is another early sign of BBS. About 90% of people with BBS will experience rapid weight gain before their first birthday, and most people will be diagnosed with obesity by the time they’re 3.
As you get older, the distribution of weight shifts. In childhood, weight distribution may be more even across the body, but it becomes concentrated around the abdomen and upper body over time.
Obesity in people with BBS can lead to other complications with age, including type 2 diabetes, high blood pressure, and heart disease. BBS itself can also contribute to heart problems, potentially compounding these effects.
Retinal dystrophy
The main feature of BBS is retinal dystrophy, or the breakdown of photoreceptors in the retina of the eye. These specialized cells are responsible for capturing incoming light and translating it into a nerve signal that is then sent to the brain for processing.
As these cells break down, you may experience a progressive loss of vision.
Vision loss in BBS typically begins with “night blindness” at around 4 to 8 years old. Over the next few years, vision loss may worsen, with peripheral vision typically affected next, followed eventually by the loss of central vision. Most people with BBS become legally blind within their teens or 20s.
This pattern of vision loss may also be referred to as retinitis pigmentosa, or RP.
Other eye problems can also develop with BBS, including:
- strabismus (“lazy eye”)
- cataracts
- glaucoma
Kidney disease
The condition may affect the kidneys in many ways. For example, they may not have a typical shape or structure, or they may not function properly. Some of these may not be easily detectable without imaging. As a result, it can be difficult to estimate the true impact of kidney disease on all who have BBS.
However, according to one
In this study, kidney disease in children was typically detected within the first year of life.
Other BBS complications, including obesity and high blood pressure, can worsen kidney disease and impaired kidney function. Certain genetic alterations linked to the condition may also increase the likelihood of various kidney malfunctions, but these relationships are not yet well defined.
Kidney disease and the associated treatment can also lead to other complications, such as infections and weight gain.
Reproductive abnormalities
BBS impairs the development of reproductive organs in
Other ways BBS affects reproductive organs include a delayed onset of puberty, ovarian cysts, and other genital anomalies, affecting both male and female sexual organs and consequently affecting menstrual regularity, sexual function, and fertility.
Pregnant people with BBS are at increased risk for serious complications and should go for regular checkups with an experienced obstetrician.
Cognitive impairment
Up to
- learning difficulties
- delayed speech or reading skills
- poor coordination or fine motor skills
- impaired social development
While many people with BBS may experience challenges in these fields, available data suggest that only about 20% to 25% will meet diagnostic criteria for an intellectual disability, with most cases typically characterized as mild to moderate in nature.
Other symptoms
Other symptoms of BBS that are less common or that develop as a result of the complications described above include:
- diabetes or other metabolic disorders
- congenital heart defects
- spasticity (muscle stiffness or spasms) or ataxia (loss of muscle coordination or control)
- liver disease or other gastrointestinal disorders
- bladder problems
- dental or facial abnormalities
- behavioral problems
BBS is typically passed down in an autosomal recessive pattern by both parents. This means that each parent has one gene with a mutation for BBS and another that isn’t mutated. Neither of them shows signs or symptoms of the condition, making them carriers of BBS.
Several genes have been linked to BBS, most named based on their association with the disease. In white, Western populations, most cases of BBS are caused by alterations in the BBS1, BBS2, or BBS10 genes.
Genetic testing can help identify the specific alteration associated with your BBS. This may be helpful in determining the outlook for the condition and any complications. However, scientists have now identified more than 20 different genes that are linked to BBS, but they haven’t yet identified any causative genes in 20% to 30% of the cases.
Estimates of life expectancy with BBS are more than 2 decades old and do not reflect advancements in the care of people with the condition. In general, scientists believe that BBS itself does not reduce life expectancy, but that complications from the condition — particularly heart or kidney disease — can be fatal.
Supportive care can help reduce the likelihood of severe outcomes with BBS complications.
Treatment for BBS is currently based on the management of symptoms. Since many organ systems may be involved, management of BBS typically involves a multidisciplinary team that includes:
- an ophthalmologist
- a nephrologist
- an endocrinologist
- a genetic counselor
Additional supportive care may be necessary, including psychological support, special education specialists, occupational therapists, and specialists to support reproductive health.
Treatment of BBS symptoms may also involve a multimodal approach consisting of:
- medications
- diet and exercise management
- behavioral, physical, or speech therapies
- mobility or accessibility aids
- surgery
You and your family may also consider participating in a clinical trial to better understand the nature of BBS and how new treatment options can affect the course of your condition.
BBS is a rare disorder affecting many organ systems, including the eyes, kidneys, brain, heart, and reproductive organs. It’s an inherited disorder, and most people with BBS have symptoms at birth or develop them within the first year of life.
Treatment involves symptom management and requires a multidisciplinary, multimodal approach to care. It’s important that you and your loved ones set up a care team early to help manage the symptoms and reduce the likelihood of additional complications. With proactive supportive care, you can live a full life with BBS.