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P. Bitoun, E. Pipiras, P. Bouchard, B. Benzacken, L. Benzacken; BBS5 Is Associated With Early Onset Severe Metabolic Syndrome, Cone Rod Dystrophy and Polydactyly. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1665.
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to further evaluate and define the impact of the rare BBS5 gene mutation on the phenotype of patients with Bardet-Biedl Syndrome
A cohort of 15 patients with BBS who gave informed consent for molecular analysis of their genotype was screened for BBS5 mutations using SSCPand sequencing, The patients were aged 2 to 31 years old with a mean age of 12 years.
One consanguineous family of 2 affected brothers of syrian origin was identified with a homozygous mutation in the initiation codon of the BBS 5 gene. This mutation predicts total abolition of the BBS5 protein synthesis.We present 20 year follow up on these patients. They presented with early visual handicap with a non progressive cone-rod dystrophy before 8 years with flat cone erg and low vision without night-blindness but slight photophobia. They also showed polydactyly, hypogonadism and morbid obesity (BMI 53 and 36). Abdominal roentgen imaging showed lobulated kidneys. They developped hypertension in early adulthood with hypertriglyceridemia,(2.5g/l and 2g/l) low HDL (0.30g/l) in both and High ldl (1.7g/l) in the younger and progressed to type 2 diabetes by the age of 28 and 30 and infertility. They had signs of insulin resistance with acanthosis nigricans at age 25. They have normal intelligence with one working in the post office and the other as an accountant. Both their heterozygote parents are overweight with hypertension.
BBS5 is one of the rarer BBS genes involving about 1,5% of BBS patients in the french cohort. The BBS 5 protein is part of the flagellar basal body apparatus.Several BBS gene polymorphisms have been associated with the metabolic syndromes BBS1, BB2, BBS4, BBS6 in the french caucasian population.BBS5 has been previously described in 4 families of newfoundland, Saudi arabian, Turkish and Kurdish descent and thus seems to be widespread in the middle east.Thus the absence of BBS5 protein seems to be involved with early and severe metabolic syndrome and may thus play a key role in the general population affected with this multifactorial phenotype.
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