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T.D. Hjorthoej, K. Grønskov, T. Rosenberg, K. Brøndum–Nielsen; Bardet–Biedl Syndrome: Does BBS2 Result in A More Serious Phenotype Than BBS1? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4621.
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Bardet–Biedl syndrome (BBS) is a complex genetic syndrome resulting in retinal dystrophy, postaxial polydactyli, obesity, hypogenitalism among males, renal manifestations, and learning disabilities. BBS shows great genetic heterogeneity: nine genes have been cloned and these account for half of the patients. BBS is an autosomal recessive disease, but triallelic inheritance has been shown in some cases. The prevalence in the general population is 1/60.000 in Denmark, whereas other countries report a lower prevalence (1/125.000).
The aim of the project was to characterise the genotypes in the Danish Bardet–Biedl population and to evaluate possible genotype–phenotype correlations.
Of 100 patients with Bardet–Biedl syndrome registered in the "Retinitis Pigmentosa Register" at the Kennedy Institute – National Eye Clinic 60 patients in 55 families gave accept to participate in our research. Clinical information was achieved from medical files and personal communication. Out of 60 patients only in one case the clinical diagnosis could not be confirmed by the criteria given by Schachat and Maumenee (Arch Ophthalmol.1982 Feb;100(2):285–8). In our study we screened for mutations in four BBS–genes (BBS1, BBS2, BBS4, MKKS) by DHPLC (denaturing high performance liquid chromatography).
In 49% of the BBS–families we identified mutations, and 42% had two or more mutations (n=23). The table shows the phenotype–genotype correlation for patients with mutations in the two major Bardet–Biedl genes, BBS1 and BBS2. In BBS2 patients all had polydactyly and obesity, more males had hypogenitalism, and a higher part learning disabilities. Kidney involvement was only seen in the BBS2 mutational positive.
Although the numbers are small, our data could indicate a more serious phenotype for BBS2 mutations compared to BBS1.
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