Beyond the Extra Digit: A Rare Case of Bardet-biedl Syndrome in a 12-Year-Old with Polydactyly, Obesity and Vision Loss

Abstract

Bardet-Biedl Syndrome (BBS) is a rare multisystem ciliopathy with autosomal recessive inheritance and genetic heterogeneity, characterised by retinal degeneration, post axial polydactyly, renal disease, hypogonadism, central obesity, several dysmorphic features and variable degrees of cognitive impairment. Our proband a 12y old male child who had presented to our institute with signs of some dehydration as a result of non-bloody diarrhea and vomiting for 3 days, was found to be having horizontal nystagmus, post axial polydactyly in right foot, obesity, pigmentary retinopathy, micropenis and vesico-ureteric reflux on ultrasonography. Considering a probable diagnosis of Bardet-Biedl Syndrome, whole exome sequencing was done which confirmed the diagnosis by identifying a homozygous splice site donor variant c.1527+1G>A in intron12 of the BBS2 gene on chromosome 16q with autosomal recessive inheritance which was classified as Pathogenic as per ACMG guidelines. Patient is currently under management with a multidisciplinary team. Frequent regular follow-up plan with teaching of braille, admission to a special education school and follow up with fundoscopy and fibro scans is being undertaken.