Barde-Beadle syndrome is a hereditary genetically heterogeneous disease, which is characterized by a combination of multiple congenital developmental defects with impaired hypothalamic functions.
A pathological state of recessive-autosomal type with variable penetrance is inherited. The medical literature describes 9 genes whose mutation is responsible for the development of this disease: BBS2 (16q21); BBS1 (11q13); BBS3 (3p12-q13); BBS5 (2q31); BBS4 (15q22.3); BBS6 (20p12); BBS8 (14q32.11); BBS7 (4q27) and BBS9 (7p14).
Children with Barde-Beadle syndrome in the photo can be seen below.
This pathology was described in 1920 by the French doctor Georges Bardé in his dissertation, and the pathologist of Hungarian origin from Austria Arthur Biedl gave a complete clinical picture of this syndrome.
For a rather long period of time, Bardet-Beadle Syndrome and Lawrence-Moon Syndrome were considered as a single nosology, however, their significant difference has recently been proved: with the latter, paraplegia is observed, and obesity and polydactyly are not found.
If you suspect the development of the described condition, it is also necessary to carry out a differential diagnosis with Alstrem syndrome, Bimond II, Frelich, Grefe-Sjogren, pseudosyndrome Frelich, Berejeson syndrome, puberty obesity.
The type of inheritance in Barde-Beadle syndrome is autosomal recessive. Some authors suggest multifactorial or dominant inheritance of the disease.
Causes of occurrence
The causes of Bardet-Beadle syndrome are still unclear. However, some scientists believe that its occurrence is due to certain gene mutations in the formation of the fetus caused by pathological heredity.
Clinical symptoms
All varieties of clinical manifestations of this pathology are huge. The most obvious of them are:
- various eye diseases (retinopathy pigmentosa, micro- and anophthalmia, iris coloboma, myopia, posterior polar cataract, primary optic atrophy of the optic nerve, epicanthus, macula underdevelopment, strabismus, external ophthalmoplegia, bilateral ptosis of the upper eyelids reduce acute vision) , and further - to complete blindness;
- syndactyly or polydactyly, abnormalities of skull formation;
- uniform pituitary obesity;
- lag in mental and physical development;
- hypogenitalism.
In addition, with Bardet-Beadle syndrome, pathologies of the cardiovascular system (dilated cardiomyopathy, left ventricular and interventricular septum hypertrophy), digestive organs (gastrointestinal fibrosis), urogenital system (urogenital sinuses, renal failure, ectopia and ectopia are common) , fallopian tubes and ovaries, vaginal septa), musculoskeletal system (dysplasia of the vertebrae and ribs, spina bifida, cleavage of the palate, etc.).
The minimum diagnostic signs are polydactyly, obesity, mental retardation, hypogonadism, retinal pigment degeneration.
For this pathological syndrome, five of the above symptoms are characteristic. However, all of them are observed in less than half of all cases of the development of the disease, in the majority of diagnoses 3 or 4 symptoms of a similar illness are noted (incomplete form).
Eye anomalies
The most common sign of Barde-Beadle syndrome is retinal pigment degeneration (in 90% of cases). With ophthalmoscopy, specialists detect pigment deposition in the peripheral areas of the retina and in the area of the optic nerve nipple. Progression of retinal degeneration leads to night blindness, and subsequently to loss of vision. 75% of patients go blind by about 20 years.
Other abnormalities of the visual organs are also described:
- macular degeneration;
- myopia;
- cataract;
- atrophy of the optic nerves;
- microphthalmos;
- nystagmus.
Obesity
Obesity with Barde-Beadle syndrome is observed in approximately 91% of patients, it develops in the 1st year of life and progresses with age. In 85% of cases, mental retardation is noted, which in some cases is combined with certain neurological symptoms, for example, spastic paraplegia, extrapyramidal and cerebellar disorders, seizures.
Postaxial polydactyly is detected in 74% of patients. It is often combined with brachydactyly and syndactyly. Other skeletal abnormalities include brachycephaly, microcephaly, and oxycephaly. Hypogenitalism is observed in approximately 66% of cases and is most often diagnosed in male patients. In boys, it can manifest itself in the form of hypoplasia of the external genital organs, cryptorchidism and hypospadias, scrotal cleavage is sometimes observed, and impotence often develops in adults. In female patients, the most frequently diagnosed are lagging in sexual development, vaginal atresia, vaginal septum and doubling of the uterus, oligo- or amenorrhea, ovarian hypoplasia.
Among the defects in the formation of internal organs, kidney diseases (cysts, dysplasia, nephrosclerosis, hydronephrosis and hydroureter, pyelonephritis and glomerulonephritis) are characteristic. In some cases, defects of the brain and heart are observed (hydrocephalus, atrophy of the grooves, agenesis of the corpus callosum, asymmetry of the hemispheres).
Diagnosis of a pathological phenomenon
The pathological process is suspected by ultrasound during intrauterine development or immediately after birth (if there is polydactyly). Often, Bardet-Beadle syndrome is diagnosed only in adolescence. This is due to the fact that the symptoms of the disease join gradually.
Treatment
At the moment, there is no specific treatment for this disease in modern medicine. Therapy is usually symptomatic. For example, obesity is treated with a special diet, and diabetes mellitus with a hypoglycemic therapy. Extra fingers and toes are removed in early childhood or infancy.
To date, several methods have been developed to prevent the progression of visual impairment as a result of pigmented retinal degeneration.
The prognosis for the described pathological conditions is quite serious: many patients die at the age of 12-20 years. The cause of death in most clinical cases is renal failure and heart defects.