Purpose
To provide the first detailed macular description in Chinese patients with Bardet-Biedl syndrome (BBS).
Methods
This study included seven male and one female unrelated Chinese patients clinically diagnosed as BBS. The patients were examined for general and ocular anomolies. High-resolution macular images were obtained by spectral domain optical coherence tomography (SD-OCT) and were compared with those of age and refraction-similar control subjects for macular thickness and structure. Changes on fundus autofluorescence (FAF), kinetic and static perimetry and electroretinography were also evaluated when available. Genetic analysis was performed using either sanger sequencing or next generation sequencing.
Results
General and ocular features required for the diagnostic criteria of BBS were found in each subject including retinitis pigmentosa (RP), nystagmus, polydactyly, obesity, overweight, intellectual disabilities, male hypogonadism, renal malformation and congenital heart defects. The median age at the onset of the visual symptoms including night blindness and decreased visual acuity was 4.0 years (range, 2-7 years). Best-corrected visual acuity (logMAR) ranged from 0.7 to 1.7. Except for the lack of bone spicule, fundus abnormalities were typical of RP shown as optic disc pallor, attenuated vessels and generalized atrophy of the retina and choriocapillaris. All of the patients showed varied degrees of macular alteration under ophthalmoscope, ranging from mottling of the macular pigment epithelium to a bull’s eye maculopathy. On SD-OCT the changes in the macula were found as epiretinal membrane as well as extensive disruptions in the outer segments, ellipsoid zone, outer limiting membrane and outer nuclear layer. Marked reduction in the macular thickness was observed when the BBS patients were compared with the healthy controls. The macular lesions were correspondingly seen as hypofluorescence on FAF. Genetic analysis demonstrated either homozygous or compound heterozygous mutations in the BBS1, BBS2, BBS4 and BBS7 gene. Six variants were found to be novel.
Conclusions
The BBS-associated RP in Chinese patients manifested obvious visual symptoms in their first decade of life, and the chorioretinopathy may be accompanied by significant macular involvement which leads to severe visual impairment in early ages.