What are the symptoms? Primary features: rod/cone dystrophy – a progressive eye condition, which can lead to blindnessobesity, childhood-onset with fat distributed particularly around the trunk (middle of body)polydactyly (extra fingers and/or toes)hypogenitalism (underdeveloped genitals)mild-to-severe learning difficulties (see entry Learning Disability)renal abnormalities (such as cysts) and impaired renal functionendocrine disturbances that involve pituitary, thyroid, adrenal glands, the ovaries and testes (may lead to subfertility). Secondary features may include: speech problemsdevelopmental delay (see entry Global Developmental Delay)behavioural abnormalitieseye abnormalities, including strabismus (cross-eyed), cataracts, and astigmatism (abnormally shaped eyeball)balance disturbance and broad gait (walking)reduced fine motor skillsbrachydactyly (short fingers and/or thumbs)syndactyly (digits joined together)diabetes mellitusdental and roof of mouth abnormalities (high-arched palate)cardiovascular anomalies (high blood pressure, abnormal heart valves)hepatic (liver) problemsolfactory dysfunction (lack of ability to smell)Situs inversus (misplacement of internal organs – eg mirror-image). In children with BBS, night-blindness usually occurs by seven to eight years of age and total blindness is typical by the third decade. What are the causes? Twenty-one genes are known to be associated with BBS. Two mutations in any one of these genes are enough to manifest the syndrome. Not all people (~15%) with BBS have mutations in these known genes, so more remain to be discovered. It is now known that these mutations result in abnormal cilia function. These are finger-like projections that are important for cells to sense their surrounding environment and communicate with one another. How is it diagnosed? Diagnosis is made on the basis of clinical features initially. A diagnosis can be confirmed by testing DNA to see if the mutation(s) causing the condition lie in one of the 21 genes already identified. How is it treated? There is no cure for BBS. Treatment aims to reduce the symptoms experienced by a person with BBS. Regular eye check-ups by an ophthalmologist will highlight any existing problems. Visual aids and educational programmes can assist with visual difficulties. Obesity is managed with diet, exercise and behavioural therapies. Hypercholesterolemia (high cholesterol) and diabetes mellitus may be treated with the appropriate medications and changes to diet. Early intervention, special education provision and speech and language therapy can help with learning. In cases of severe renal (kidney) abnormality, renal transplantation may be required. Genital abnormalities, for example hypospadias, may be surgically corrected. Hormone replacement therapy can be initiated for hypogonadism (where sex glands produce little or no sex hormones). Cardiac abnormalities need to be monitored and may be corrected surgically. Surgery to remove extra digits prevents difficulties walking and balancing and poor fitting of footwear. Inheritance patterns and prenatal diagnosis Inheritance patternsInheritance is autosomal recessive (two mutations required to manifest the disease). Prenatal diagnosisA number of features (e.g. extra digits, hyperechogenic kidneys) can be determined on high-definition ultrasound scanning of the fetus. This, however, is not a test of exclusion of the condition. If two gene mutations can be identified in a BBS family then a molecular genetic DNA test can be offered prenatally. Is there support? Bardet-Biedl Syndrome UK (Formerly LMBBS) Tel: 07591 206680Email: firstname.lastname@example.orgWebsite: bbsuk.org.uk The charity is a Registered Charity in England and Wales No. 1027384 and in Scotland No. SCO41839. It provides information and support for people with Bardet-Biedl Syndrome and their families and carers throughout the UK. The Charity holds an annual family conference and activities throughout the year and through the BBS UK Clinics provides further support and facilitation services alongside the NHS. Group details last updated April 2018.