Bardet-Biedl syndrome (BBS) is a rare genetic condition that affects multiple organs and causes a wide range of symptoms, starting in infancy or early childhood. Learn more about its symptoms, causes, outlook, and treatment options.

Symptoms of BBS may be apparent prenatally or may not begin until as late as 10 years.

The number of people living with BBS ranges from about 1 in 100,000 to 1 in 250,000 globally. Some specific regions experience a significantly higher prevalence, such as certain populations in Kuwait, Newfoundland, and the Faroe Islands.

People assigned male and female at birth have equal chances of inheriting BBS.

BBS and Laurence-Moon syndrome are separate and distinct conditions, but doctors previously treated them as a single condition called Laurence-Moon-Biedl-Bardet syndrome. People may come across this term in some outdated materials.

There are six primary symptoms of BBS. Not everyone with BBS will have all of these symptoms, but they will need three to four for a clinical diagnosis. The primary symptoms are:

  • obesity, especially around the torso and abdomen
  • visual impairment
  • learning disabilities
  • polydactyly (extra fingers or toes)
  • kidney issues
  • hypogonadism (sex glands produce reduced or no hormones)

Below are descriptions of the six primary symptoms of BBS and how they typically manifest. For a diagnosis of BBS, a person must have at least four of these primary symptoms or three primary symptoms along with two secondary symptoms.

Obesity

Obesity is a primary symptom of BBS and is often apparent by 1 year old. Excess weight generally accumulates in the abdominal and torso areas. This may be accompanied by — or the result of — excessive hunger and eating. It is not unusual for people with BBS to develop type 2 diabetes, and obesity can be a contributing factor.

Visual impairment

For some people, visual impairment is the first indication of BBS, often beginning as night blindness — or difficulty seeing in dim lighting — beginning between the ages of 4 and 8 years. Vision loss may continue, with a person losing peripheral vision first. Vision often deteriorates to the level of legal blindness, but this is not always the case.

Learning disabilities

Learning disabilities can be a symptom of BBS. When checking for learning disabilities, it is important to determine that the issue is truly an independent symptom and not simply a result of visual impairment, which is a primary symptom in its own right. Some examples of learning disabilities include delayed speech or impaired attention capacity.

Polydactyly

Polydactyly is a condition in which a person has extra or partial digits on their hands, feet, or both. As with the other symptoms of BBS, polydactyly can be present on its own or be a symptom of many other conditions, so it does not indicate BBS by itself.

Kidney issues

There are many types of kidney issues that a person with BBS might experience. Some people may have abnormalities in the shape, size, or location of their kidneys, or they may be missing one or both kidneys entirely. Others may have one of many kidney diseases that affect proper functioning.

Hypogonadism

Hypogonadism or other abnormalities related to sex organs, such as testicles or the uterus, are frequent in people with BBS. This can lead to various issues, including difficulty reproducing, but there are cases of both males and females with BBS having biological children.

The secondary symptoms of BBS can include:

  • speech delay
  • developmental delays
  • behavioral or neurological issues
  • metabolic syndrome
  • type 2 diabetes
  • hypothyroidism
  • polycystic ovarian syndrome
  • facial abnormalities
  • vision problems
  • high blood pressure
  • congenital heart disease
  • hearing impairment
  • dental crowding
  • reduced or missing sense of smell
  • flat or wide feet, no arches, or abnormal gait
  • liver disease
  • gastrointestinal disease

BBS follows an autosomal recessive pattern of inheritance.

This means a person needs two copies of a mutated gene to develop BBS. If someone only has one mutated copy of the relevant gene, they are known as a “carrier,” meaning they do not have BBS and do not experience any outward symptoms.

If one biological parent is a carrier and the other is not, none of their offspring will have BBS, but 50% are also likely to be carriers.

If both biological parents are carriers, each offspring has a 25% chance of having BBS, a 50% chance of being a carrier, and a 25% chance of having no mutated gene at all.

If a person suspects either they or their partner may be carriers of BBS, genetic counseling may be available to provide more detailed information for their specific circumstances.

BBS does not necessarily affect life expectancy, but this will depend on the severity of each individual’s symptoms. Kidney diseases and obesity, in particular, can lead to additional health problems that may need close management.

There is currently no cure for BBS. Treatment generally centers on treating the symptoms and can include anything from corrective eyewear to dialysis or surgery.

People may be interested in learning more about or participating in clinical trials.

Perhaps the most effective step for people with BBS and their families is to form connections with the BBS community. Others affected by this condition may be able to provide information, tips, and emotional support.

A person’s doctor, specialist, or pediatrician can provide medical guidance on prioritizing treatment options.

BBS is a rare inherited genetic disorder with a wide variety of possible symptoms. The composition and severity of these symptoms are unique to each individual.

The main treatment goal is to minimize the effects of the symptoms. It is possible to live a full life while having BBS.