Bardet-Biedl syndrome is a ciliopathy mainly associated with retinal dystrophy, renal dysfunction, post-axial polydactyly, obesity, cognitive deficit and hypogonadism. The symptoms associated with retinal dystrophy do not usually appear until the first decade of life, so the diagnosis is usually delayed. Ocular involvement may be the initial form of manifestation of this syndrome, it may even be the only one, so it should be taken into account in the differential diagnosis of amblyopia in a child who does not improve despite correct compliance with treatment. A case of low visual acuity in a pediatric patient is presented as an initial manifestation that leads to the diagnosis of Bardet-Biedl Syndrome, and which is also the only symptom that the patient presents to date, despite being a multisystem disease.

OBJECTIVE: Bardet-Biedl syndrome (BBS) is a multisystemic genetic disorder, which is not widespread among the Caucasian population, characterized by a highly variable phenotype and great genetic heterogeneity. BBS belongs to a group of diseases called ciliopathies, caused by defects in the structure and/or function of cilia. Due to the diagnostic complexity of the syndrome, the objective of this study was to analyse our whole group of patients in order to create an algorithm to facilitate the routine molecular diagnosis of BBS. We also calculated several epidemiological parameters in our cohort.
METHODS: We analysed 116 BBS patients belonging to 89 families from the whole Spanish geography. All probands fulfilled diagnosis criteria established for BBS. For this, we used: genotyping microarray, direct sequencing and homozygosis mapping (in consanguineous families).
RESULTS: By means of the different approaches, it was possible to diagnose 47% of families (21% by genotyping microarray, 18% by direct sequencing of predominant BBS genes, and 8% by homozygosis mapping). With regard to epidemiological data, a prevalence value of 1:407,000 was obtained for BBS in Spain, and a sex ratio of 1.4:1 (men:women).
CONCLUSIONS: The proposed algorithm, based on the analysis of predominant BBS genes combined with homozygosis mapping, allowed us to confirm the molecular diagnosis in a significant percentage of families with clinically suspected BBS. This diagnostic algorithm will be useful for the improvement of the efficiency of molecular analysis in BBS.