Bardet-Biedl syndrome was first described by doctors Bardet and Biedl in the 1920s. Bardet-Biedl syndrome is a condition that affects many parts of the body. The primary symptoms are polydactyly (extra fingers and/or toes), obesity and cone-rod dystrophy resulting in severe visual impairment. However, Bardet-Biedl syndrome has a range of other features that vary greatly between patients and in severity, even among family members. The rare syndrome is probably under-diagnosed. The treatment is multidisciplinary and is mainly symptomatic, supportive and relieving.
- Clinical overlap
- Epidemiology Bardet-Biedl syndrome
- Causes and heredity
- Symptoms: Skeleton, weight, eyes and development
- Diagnosis and examinations
- Therapy
- Prognosis
- Rare disease contact group
Clinical overlap
Some scientists claim that Laurence-Moon syndrome is the same as Bardet-Biedl syndrome which was first described in the medical literature by physicians Laurence and Moon in 1865. Bardet-Biedl syndrome does indeed overlap with Laurence -Moon syndrome, but LM patients often do not suffer from polydactyly and obesity, but do suffer from paraplegia (paralysis of the lower body with loss of sensation). However, scientists do not yet agree on whether the two conditions are the same. Further research is required for this.
Epidemiology Bardet-Biedl syndrome
The prevalence of BBS varies widely between populations. The prevalence is estimated at 1 in 100,000 and 1 in 175,000 in the unrelated population of Northern Europe and America. The condition is more common on the island of Newfoundland (off the east coast of Canada), where it affects an estimated 1 in 17,000 newborns. The condition occurs with greater frequency in the Bedouin population of Kuwait (1 in 13,500). Bardet-Biedl syndrome affects men and women equally. Information about gender preference is not known.
Causes and heredity
The cause of Bardet-Biedl syndrome is a gene mutation. About 25% of all cases are due to mutations in the BBS1 gene; in 20% the cause is a mutation of the BBS10 gene. The other BBS genes each account for only a small percentage of all cases of this condition. In approximately 25% of patients with Bardet-Biedl syndrome, the cause of the disease is unknown. Most cases of Bardet-Biedl syndrome occur spontaneously, but the inheritance pattern is sometimes also autosomal recessive.
Symptoms: Skeleton, weight, eyes and development
A lot of symptoms are possible with this syndrome. These are determined individually and differ in degree of severity per person. Some primary symptoms are present such as polydactyly, obesity and cone-rod dystrophy.
Skeleton
The polydactyly focuses on the hands and feet. In approximately 70% of all patients there is an extra finger at the little finger or an extra toe at the fifth “little” toe. Syndactyly (fused fingers or toes) and bifurcated dactyly (abnormally short fingers or toes) have also been reported.
Weight
In addition, severe obesity occurs in Bardet-Biedl syndrome. The abnormal weight gain usually begins in early childhood and remains a problem throughout life. The patient has felt excessive hunger, which is known as “polyphagia”. This sometimes results in type 2 diabetes mellitus, high blood pressure (hypertension), and abnormally high cholesterol levels (hypercholesterolemia).
Eyes
Rod-cone dystrophy, also known as retinal degeneration or retinitis pigmentosa, leads to vision loss. Vision loss occurs when the light-sensitive cells at the back of the eye (the retina) gradually die. Visual impairment starts in childhood with night blindness because the rods that ensure vision in the dark die. Photophobia (photophobia) and loss of color vision usually follow. The cones slowly die and they are responsible for color vision. In the next phase, blind spots (scotomas) develop on the peripheral side (side) that expand over time. This causes tunnel vision, causing the patient to have to look through a tube, as it were, which keeps getting smaller. Most patients with Bardet-Biedl syndrome also experience blurred vision in the central part (poor visual acuity). The eye disease is so progressive that most patients are already blind in adolescence or young adulthood. Other eye abnormalities such as strabismus, cataract (clouded eye lens), glaucoma (increased intraocular pressure, which the ophthalmologist measures via tonometry), nystagmus (involuntary rhythmic movements of the eyes) and refractive errors such as myopia (nearsightedness) have also been reported in the Bardet-Biedl- syndrome.
Development
Other major symptoms of Bardet-Biedl syndrome include intellectual disability or learning difficulties . Abnormalities of the genitals are also possible. Some men suffer from hypogonadism (insufficient development of gonads), which usually makes them infertile (male infertility). Drinking a lot and urinating a lot are sometimes also secondary symptoms. Many patients with Bardet-Biedl syndrome also often have serious and life-threatening kidney abnormalities.
Additional symptoms
In addition, a number of other symptoms are possible: clumsiness or coordination problems, impaired speech, delayed motor development such as standing and walking, and behavioral problems such as outbursts and emotional immaturity. Facial abnormalities, dental abnormalities, unusually short or deformed fingers and/or toes, spasticity and partial or complete loss of the sense of smell (anosmia) have also been reported in some patients. In addition, this condition may affect the heart (left ventricular hypertrophy), the liver (liver fibrosis), and the digestive tract. Mild hearing impairment and ear infections have also been reported in about half of patients with Bardet-Biedl syndrome.
Diagnosis and examinations
Bardet-Biedl syndrome is often difficult to diagnose. A doctor does not immediately link a child born with polydactyly to the condition. Only when eye problems and obesity occur in early childhood does the doctor make a link with the syndrome. The diagnosis is then based on the main symptoms (visual problems due to retinal dystrophy (medical term for “retinal degeneration”), obesity and polydactyly). The ophthalmologist performs a comprehensive eye examination for retinal degeneration, usually via an electroretinography (ERG), a test that measures the electrical response of the retina to a light stimulation source. Furthermore, a DNA test is possible, but this will not always yield results as the cause of the syndrome is unknown in a number of patients.
Therapy
There is no specific treatment available, but the symptoms can be treated individually per patient with existing multidisciplinary therapies. The following healthcare professionals are involved: pediatricians, orthopedic surgeons, cardiologists, dentists, dieticians, speech therapists, audiologists, ophthalmologists, nephrologists, endocrinologists. Regular comprehensive examinations by an ophthalmologist, a nephrologist and an endocrinologist are recommended. Regular blood pressure checks are also necessary. Hormone treatment is sometimes required to stimulate the development of the sexual organs. Finally, surgery is possible to remove the extra fingers or toes.
Prognosis
The eye disease is progressive; the visually impaired person becomes completely blind.
Rare disease contact group
Loss of vision, mental and social development problems, kidney abnormalities, underdeveloped sexual organs, obesity and skeletal abnormalities (extra fingers & toes) are characteristic of Bardet-Biedl syndrome. The Bardet-Biedl Foundation, which was founded in June 2017, aims to improve and increase awareness, care and research of the syndrome.
Bardet-Biedl StichtingZwarte Zeestraat 448303 EW EmmeloordE-mail: [email protected]: http://www.bardetbiedl Syndrome.nl/Facebook: https://www.facebook.com/pg/BardetBiedlStichting/
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