Patient Information Sheet: Bardet-Biedl syndrome
What is Bardet-Biedl Syndrome?
A syndrome is the name given to a condition where features occur in a consistent pattern, and where the cause is not understood. Bardet-Biedl syndrome (BBS) is named after Georges Louis Bardet, a French physician (born 1885) and after Artur Biedl, a Hungarian pathologist and endocrinologist (born 1869). Since the original descriptions, over 200 patients have been described in the world medical literature.
How common is it?
Bardet-Biedl syndrome affects about 1 in 160,000 people, so it is very rare. A specialist physician may only see one affected child in a professional lifetime.
What may happen in the condition?
Some children are born with extra fingers or toes. These are usually removed soon after birth, but sometimes can be associated with Bardet-Biedl syndrome.
Children may develop early onset obesity, which unfortunately is often blamed on a poor diet. It is however part of the condition. This can lead on to fatty liver disease in late childhood.
Some babies have cystic kidneys which are detected antenatally or in early childhood. This can lead to chronic renal failure, which needs treatment.
Retinal Dystrophy means abnormalities of the rods and/or cones at the back of the eye. Symptoms often present as ‘wobbly eyes’ in infancy. There is unfortunately no treatment for this.
Diabetes mellitus is the name given when the body cannot convert glucose or sugar to energy, because the insulin from the pancreas is not working effectively. Symptoms include thirst and frequent passing of urine, and weight loss. Glucose is passed out in the urine, and blood tests show a high level of glucose in the blood. This usually needs treatment with tablets or insulin injections.
Deafness usually means difficulty in hearing in a crowded room, and difficulty hearing high pitched sounds. Some people are helped with a hearing aid.
Some children with Bardet-Biedl syndrome have moderate learning difficulties and need extra support at school.
How do I tell if my child has the condition?
Usually children present with retinal dystrophy and early onset obesity. If a young person does not have retinal dystrophy by later childhood, he/she is unlikely to have Bardet-Biedl syndrome. However, the diagnosis is sometimes missed and can be made much later.
What is the outlook for a child with Bardet-Biedl syndrome?
The diabetes mellitus can be controlled with insulin injections. The vision problems usually, but not always, get worse, and often a person may be registered blind by early adulthood. Many young people get deafness. Many also get renal problems in early childhood and may eventually need treatment for this.
What are the chances of having another affected child?
Although it had been originally thought to be a recessive disorder, it has been demonstrated that some forms of Bardet-Biedl syndrome require more than one mutation in more than one gene locus. This has been called ‘triallelic inheritance’, or ‘recessive inheritance with a modifier of penetrance. So for a child to be affected, he/she has to inherit sometimes several abnormal copies of two or more BBS genes. It is possible to test if an unborn child is affected during pregnancy.
Will there be a cure for Bardet-Biedl syndrome?
Any cure is a long way off. The current research is to understand why mistakes in the BBS genes cause the syndrome. There are research groups in America, France and the UK, all investigating this problem.
Who can I go to for help?
There is a good review in Gene Reviews written by Professor Beales (http://www.ncbi.nlm.nih.gov/books/NBK1363/). It is also very important that you show this leaflet to your doctor so that he knows what information you have. If you have any questions about the information in this leaflet, please write to me and I will try and answer.
This information leaflet is a draft until a more detailed and definitive leaflet is developed as part of the EURO-WABB project
Dr Timothy G Barrett
Professor of Paediatrics
C/O Diabetes Unit
Birmingham Children’s Hospital
Birmingham B4 6NH