Clinical characteristics and ultra-widefield fundus image analysis of two siblings with Bardet-Biedl syndrome type 1 p.Met390Arg variant

Abstract

Purpose: To present the case of two siblings with a genetic diagnosis of Bardet Biedl syndrome (BBS) type 1, yet different clinical profiles and disease manifestations. Observations: Sequencing analysis revealed a p.Met390Arg pathogenic variant in the BBS1 gene of both patients, as well as several additional variants of uncertain significance Patient 1 was 41 years old, had three primary (cone-rod dystrophy, hypogonadism, and truncal obesity) and three secondary (arterial hypertension, strabismus, and astigmatism) BBS features. He also had insulin resistance, as well as low levels of total testosterone and cortisol. Patient 2 was 43 years old, had two primary (cone-rod dystrophy and truncal obesity), and four secondary (arterial hypertension, diabetes mellitus, strabismus, and astigmatism) BBS features. Both patients had severe maculopathy; however, patient 1 had bone-spicules that extended up to the mid-periphery, in a perivenular pattern, and significant vascular attenuation with “ghost vessel” appearance towards the temporal periphery, a feature that was absent on patient 2. Conclusions and Importance: The intrafamilial phenotypic variability among our patients supports the hypothesis that BBS is a disease with genetic, hormonal, and environmental triggers interacting to produce phenotypic variability. Although our report may not establish a definite relationship between environmental and genetic influences, their role should be explored in future studies.

Keywords

• Bardet biedl syndrome
• Cone-rod dystrophy
• Ophthalmic genetics
• Retinitis pigmentosa