Laurence-Moon-Bardet-Biedl syndrome (LMBBS) is an autosomal recessive genetic disorder characterized by obesity, retinal degeneration, extra digits on the hands and feet, and intellectual impairment. In an autosomal recessive disorder, both parents must be carriers of the defective gene and both must pass on the defect to the child in order for the child to be affected. If both parents carry the defective gene responsible for causing LMBBS, they have a 1 in 4 chance of having a child with the syndrome.
In 1993, the gene responsible for LMBBS was located on chromosome 16q21 (type 2). Shortly thereafter, another gene on chromosome 11q13 (type 1) was identified. Since then, two others were found on chromosomes 3p12 (type 3) and 15q22 (type 4). The most common form of LMBBS is type 1 and the most rare form is type 3. It is expected, however, that another gene that causes the syndrome also exists because there are identified cases that have none of these four defects. The occurrence rate varies in different parts of the world. In regions such as Kuwait, the occurrence is 1 in 13,500 due to a high frequency of inter-family marriages. British studies, on the other hand, show the prevalence to be 1 in 160,000. While this syndrome is considered rare, it is suspected that there is a major problem with under-diagnosis.
There has been ongoing confusion as to whether LMBBS should be described instead as two distinct disorders: LMS and BBS. In the late 1800's, two physicians named John Z. Laurence and Robert Moon described four out of eight siblings who had retinitis pigmentosa, lack of intelligence, short stature, spastic paraparesis, and hypogenitalism in the males. In 1920, Dr. George Bardet submitted a thesis on hypothalamic obesity and noticed that a number of the cases examined had hexadactyly, retinitis pigmentosa, and obesity. Then, in 1922, Dr. Artur Biedel published an account of siblings with retinitis pigmentosa, polydactyly, and intellectual impairment. As a result, in 1925, it was decided that the conditions described by all of these physicians were the same and the disorder was named Laurence-Moon-Bardet-Biedl syndrome (LMBBS). Recently, however, the syndrome was split into Laurence-Moon (LMS) and Bardet-Biedl (BBS), where LMS is characterized as the cases involving mental retardation and spastic paresis and BBS involved obesity, polydactyly, and learning disabilities. It has been shown that BBS represents the majority of published cases.
Features and Characteristics
Following is a list of characteristics that have been seen in children with LMBBS. Not all children will exhibit all of these features:
- Rod-cone dystrophy (retinitis pigmentosa)
- Optic atrophy
- Macular dystrophy
- Polydactyly (extra fingers and toes)
- Brachydactyly (short, stubby fingers and toes)
- Syndactyly (webbing of the toes)
- Obesity (excess weight gain begins around ages 1 to 2 years)
- Learning disabilities
- Developmental delay (delay in sitting, standing, and walking)
- Speech delay
- Behavioral difficulties
- Kidney abnormalities
- Hepatic fibrosis
- Hypertension (likely a consequence of obesity)
- Diabetes mellitus
- Small penis
- Undescended testes
- Infertile males
- Unusually short tooth roots
- Short stature
- Ataxic gaits
- Deep-set eyes
- Premature frontal balding in adult males
It is often times very difficult to diagnose LMBBS. The diagnosis is first considered when a child is born with polydactyly. The diagnosis is usually made, however, when visual problems and obesity are noted. Following are the diagnostic criteria:
Primary Features (4 of these symptoms must be present for a diagnosis or 3 Primary and 2 Secondary, as shown below):
- Rod-cone dystrophy
- Learning disabilities
- Hypogonadism in males
- Renal anomalies
- Speech disorder
- Developmental delay
- Poor coordination/clumsiness
- Diabetes mellitus
- Left ventricular hypertrophy
- Hepatic fibrosis
There is no cure for LMBBS, therefore, treatment focuses on managing the symptoms. For example:
- Vision impairments - Low vision aides and mobility training are beneficial.
- Obesity - A dietician can work with the family to create an appropriate diet regimen.
- Speech disorder - Speech therapy can help children with their communication skills and parents can be taught exercises to use at home to improve their childs ability to communicate.
- Kidney problems - There are several types of kidney problems associated with LMBBS and the treatment varies accordingly. Kidney issues can be treated with medications and in rare instances, surgery (transplantation).
- Polydactyly - Skin tags can be tied off at birth and extra digits can be removed surgically.
Sabrina was diagnosed with Bardet-Biedl syndrome when she was just 2-years-old. She was born with 12 perfectly formed toes and one extra finger which was really not much more than a skin flap. The extra finger was tied off at 3 months and the toes were surgically removed when she was 6 months. We did not know that there was anything "wrong" with Sabrina until she was about 19 months old and not yet walking. This is when the doctor sent us to the orthopedist, who determined that she had hypotonia. From the orthopedist, we saw a developmental delay specialist who saw nothing wrong with her. We then made an appointment with early intervention, who determined she had a 40-50% global delay and we started services with them.
Two weeks before her 2nd birthday, Sabrina started walking unaided. Shortly thereafter, we started speech therapy because she was non-verbal - she had no receptive OR expressive speech.
All this time we had been surfing the Internet for a diagnosis because nobody seemed able to tell us what was wrong with our darling. On the Internet, I was able to match her symptoms with Bardet-Biedl syndrome and I contacted a lady who has a website up with families who battle this syndrome. I asked her how the diagnosis was made, and she forwarded my questions to the authority on Bardet-Biedl, Dr. Richard Lewis in Houston. With his help, we were able to request specific testing, which led to the diagnosis.
Sabrina has a form of retinitis pigmentosa and she is going blind. She is currently night blind and has problems with her vision in all low-light areas. Since she is pretty much non-verbal, she expresses herself by crying. She also has kidney failure, which is currently controlled by medication.
On her third birthday, Sabrina "graduated" from early intervention, and she will be starting school in August. Among other things, she will be receiving cane training so she will be able to walk independently when she is totally blind. She also gets hippotherapy. She loves her horses and looks forward to her riding lessons.
Soon we will be taking some long trips with Sabrina, to show her the beauty of this country before she goes totally blind. We want to give her every experience within our power so she can have the memories when her vision fails her.
Sabrina is very loving and loves to cuddle her family and her Pooh and Tigger and her Teletubbies. - Claudia Parker
Almost three years ago, my daughter, Liz, was born with "multiple congenital anomalies" (such as extra fingers, palmer creases, large soft spot, and frog leg positioning). Our neonatal doctor referred us to the genetic clinic of our local children's hospital. The first round of testing did not return a diagnosis. We returned six months later and still could not get Liz diagnosed.
The genetic doctors referred Liz to an early intervention program for her gross motor delays. She was now 6 months old and still wasn't sitting up. The director of the early intervention program told me of a genetic doctor, Dr. Holly Ardinger, at the University of Kansas Medical Center. She told me that the doctor was very thorough and would continue until she could give us an answer whether it was genetic or not.
We switched genetic doctors and forwarded all of Liz's medical records. In the meantime, Liz had to have ear tubes. Prepping for surgery, we discovered that Liz had a low oxygen saturation level and the anesthesiologist had us find out the cause before doing the surgery.
This lead us to a pulmonary doctor and then a cardiologist. We eventually found two heart defects; an atrial septal defect and venous vein, causing the low oxygen saturation level. This was a crucial piece to Liz's puzzle. Based on a feeling from our orthopedic doctor, Liz also had a kidney ultrasound, which detected a renal anomaly; this was another piece to the puzzle.
During our first visit with the new genetic doctor, she was able to rule out several syndromes that she was looking at but didn't come up with a definite syndrome. With these two new crucial pieces and genetic retesting at a higher band level, Dr. Ardinger ruled out some possible syndromes and she started focusing on Laurence-Moon-Bardet-Biedl syndrome (LMBBS).
At 17 months old, Dr. Ardinger diagnosed Liz with probable LMBBS (pending the change in eyesight which occurs at an average age of 9 years) based on having three primary features (polydactyly, learning disabilities, and renal anomalies) and seven secondary features (speech disorder, brachydactyly, developmental delay, ataxia, poor coordination, left ventricular hypertrophy, and spasticity).
Liz is currently receiving nine hours of early intervention which consists of physical therapy, speech therapy, occupational therapy, and special instruction. This has truly made a big difference in the development and maturity of Liz.
Earlier this month, we successfully corrected Liz's two heart defects by open heart surgery. She is such a fighter and pulled thru beautifully. Next spring, Liz will need surgery to correct a tethered spinal cord, which might be linked to this syndrome. - Maureen Hannoun
If you are interested in meeting other parents who have a child with Laurence-Moon-Bardet-Biedl syndrome, please visit the LMBBS Network at: http://www.geocities.com/HotSprings/Spa/1761.
For more information on Laurence-Moon-Bardet-Biedl syndrome, please see the following references:
- UMDS, Prince Philip Research Laboratories http://www.isgrd.umds.ac.uk/laurence/laurence2.htm
- The Foundation Fighting Blindness http://www.blindness.org/bardet.html
- Online Mendelian Inheritance in Man (OMIM)
The Disorder Zone has been created for educational purposes only and is not intended to serve as medical advice. The information provided in The Zone should not be used for diagnosing or treating a health problem or disease. It is not a substitute for professional care. If your child has any health concerns, please consult your health care provider.
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