Clinical phenotype and genotype analysis of retinitis pigmentosa sine pigmento caused by BBS gene mutations
10.3760/cma.j.cn511434-20240929-00364
- VernacularTitle:BBS基因突变致无色素性的色素性视网膜炎临床表型和基因型分析
- Author:
Zijie CHEN
1
;
Yufei TAO
;
Yun WANG
;
Qinyu HUANG
;
Mingmin YANG
;
Xuyang LIU
;
Ning FAN
Author Information
1. 厦门大学附属厦门眼科中心, 厦门 361000
- Publication Type:Journal Article
- Keywords:
BBS7 gene;
BBS2 gene;
Retinitis pigmentosa;
Bardet Biedl syndrome
- From:
Chinese Journal of Ocular Fundus Diseases
2025;41(3):178-185
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To observe and analyze the pathogenic genes and clinical phenotype characteristics of retinitis pigmentosa sinepigmento(RPSP).Methods:A retrospective clinical study. Two patients (proband) and five family members from two RPSP families admitted to Xiamen Eye Center of Xiamen University in December 2022 and Shenzhen Eye Hospital in July 2023 were included in the study. Two families have no blood relationship and were both Han Chinese. Detailed ocular and systemic medical history and specialized examinations were performed for all members, including color fundus photography, fundus autofluorescence (FAF), and full field electroretinogram (ff-ERG) examination. The peripheral venous blood of all members was collected, and genomic DNA was extracted. Pathogenic genes and their loci were screened using whole exome high-throughput sequencing technology. Sanger sequencing was used to verify the pathogenic genes in the two pedigrees. The pathogenicity of candidate variants was evaluated according to the American Society for American College of Medical Genetics and Genomics (ACMG) classification criteria and guidelines for genetic variants.Results:The two probands were male, aged 9 and 7 years, respectively. The main complaint was poor binocular vision for 6 and 3 years and poor treatment effect of amblyopia. The proband (Ⅱ2) in family 1 had a pale red color on the optic disc, with leopard-like changes in the posterior pole and thinner retinal arteries. FAF showed mottled fluorescence attenuation outside the macular vascular arch. There was no significant waveform in both bright and dark visual responses of ff-ERG. He also had 6-toed deformity of both feet, renal cysts, and a slightly overweight body. The clinical diagnosis was non-pigmentary retinitis pigmentosa. The proband of family 2 (Ⅱ1) had poor binocular vision in a dark environment and had atrophy lesions on the nasal side of the optic disc and leopard print like changes in the fundus. FAF showed uneven enhancement in the fovea. ff-ERG showed severe abnormalities in dark and light response, with significant decrease and delay in b-wave amplitude and latency. He had no other systemic abnormalities. The clinical diagnosis was binocular RPSP. There were no abnormal ocular and systemic manifestations in the two family members. Gene sequencing revealed a homozygous mutation (c.534+1G>T) of BBS2 gene, which was inherited from the mother and father respectively. Based on clinical manifestations and genetic testing results, the final diagnosis was Bardet Biedl syndrome. The genetic sequencing results confirmed a novel compound heterozygous mutation (c.950T>G: p. Leu317Arg missense mutation and c.849+1G>C splicing mutation) of BBS7 gene. His father (Ⅰ1) and mother (Ⅰ2) carried M1 heterozygous variants. Combined with the clinical manifestations and genetic testing results, the final diagnosis was Bardet-Biedl syndrome (BBS). Family 2 proband (Ⅱ1) carried the BBS7 gene C.950T>G (p.Leu317Arg) (M2) missense variation and C.849 +1G>C (M3) splice site variation. His father (Ⅰ1) and mother (Ⅰ2) carried M3 shear site variation and M2 missense variation, respectively. The two families all fit the autosomal recessive inheritance pattern, and the genotype and clinical phenotype were coseparated. According to ACMG guidelines, M1, M2 and M3 were all identified as possible pathogenic variants. Conclusions:BBS2 gene M1 homozygous variation and BBS7 gene M2, M3 complex heterozygous variation are the possible pathogenic genes in family 1 and family 2, respectively. Two families are affected by BBS and RPSP, respectively.
