Familial autosomal recessive bestrophinopathy: identification of a novel variant in BEST1 gene and the specific metabolomic profile

Multimodal imaging and genetic characteristics of autosomal recessive bestrophinopathy

PURPOSE

To report the ocular manifestations, multimodal imaging characteristics and genetic testing results of six patients with autosomal recessive bestrophinopathy (ARB).

METHODS

This was an observational case series including 12 eyes of 6 patients who were diagnosed with ARB. All patients underwent a complete ophthalmic examination including refraction, slit-lamp biomicroscopy, dilated fundus examination, fundus autofluorescence, optical coherence tomography and electrooculography. BEST1 gene sequencing was also performed for all patients.

RESULTS

The mean age was 22.8years and the male-female ratio was 0.50. All ARB patients had a hyperopic refractive error. A spectrum of fundus abnormalities, including multifocal yellowish subretinal deposits in the posterior pole, subfoveal accumulation of vitelliform material and cystoid macular edema, was observed. Fundus autofluorescence imaging demonstrated marked hyperautofluorescence corresponding to the yellowish subretinal deposits. Optical coherence tomography revealed serous retinal detachment, intraretinal cysts, brush border appearance caused by elongation of the outer segments of photoreceptors, and hyperreflective dome-shaped deposits at the level of the retinal pigment epithelium. Fundus fluorescein angiography showed hyperfluorescence with staining of the yellowish subretinal deposits. Electrooculography showed reduced Arden ratio in all patients. In addition, biallelic pathogenic variants in the BEST1 gene were detected in all patients.

CONCLUSION

ARB is a rare autosomal recessive inherited retinal disorder with biallelic pathogenic variants in the BEST1 gene and may present with a wide range of ocular abnormalities that may not be easily diagnosed. Multimodal retinal imaging in conjunction with EOG is helpful to establish the correct diagnosis.

Comprehensive Genetic Analysis Unraveled the Missing Heritability and a Founder Variant of BEST1 in a Chinese Cohort With Autosomal Recessive Bestrophinopathy

Purpose

To describe the genetic landscape of BEST1 for a large Chinese cohort with autosomal recessive bestrophinopathy (ARB), identify the missing heritability, and report a common Chinese founder variant.

Methods

We recruited 65 patients from 63 families with a clinical diagnosis of ARB. All patients underwent ophthalmic examinations and comprehensive genetic analyses, including Sanger DNA sequencing of BEST1 and whole genome sequencing (WGS). The effects of deep intronic variants (DIVs) on splicing were assessed using in vitro splicing assays in HEK293T cells and patient-derived peripheral blood mononuclear cells. Haplotype mapping was performed for 17 unrelated patients harboring variant c.867+97G>A.

Results

We identified 54 distinct disease-causing variants of BEST1 in 63 pedigrees, 62 probands with biallelic variants, and one family with monoallelic variants. Sanger DNA sequencing of BEST1 initially detected 51 variants in 61 pedigrees, including 19 probands with one heterozygous variant. Subsequent WGS, combined with supplementary Sanger sequencing, revealed three missing DIVs (c.1101-491A>G, c.867+97G>A, and c.867+97G>T) in 20 families. The novel DIV c.1101-491A>G caused an abnormal splicing resulting in a 204-nt pseudoexon (PE) insertion, whereas c.867+97G>A/T relatively strengthened an alternative donor site, resulting in a 203-nt intron retention (IR). The PE and IR generated a premature termination codon downstream. Haplotype analysis identified c.867+97G>A as a common founder variant with an allele frequency of 16%.

Conclusions

Our results expand the pathogenic variant spectrum of BEST1, and DIVs can explain almost all of the missing heritability. The c.867+97G>A DIV is a common founder variant for Chinese patients with ARB.

Twelve-year follow up of a case of autosomal recessive bestrophinopathy with transient resolution of retinal edema in one eye

PURPOSE

To report 12-year follow-up of a patient with ARB.

CASE REPORT

A 25-year-old man presented with blurred vision in his both eyes (OU). Best-corrected visual acuity (BCVA) was 20/63 Snellen equivalent in the right eye (OD) and 20/32 Snellen equivalent in the left eye. The intraocular pressures and anterior segment examination were unrevealing in OU. Posterior segment examination revealed multiple yellowish flecks and dots in the posterior pole in OU. Optical coherence tomography (OCT) showed subretinal fluid (SRF), intraretinal hyporeflective spaces, elongated and shaggy photoreceptors and outer retinal defects. Fundus autofluorescence demonstrated mottling hyperautofluorescence and hypoautofluorescence in the posterior pole in OU. Fluorescein angiography illustrated hyperfluorescence in the posterior pole and surrounding the arcades in OU. Multifocal electroretinography objectified mild to markedly abnormal responses in all ring areas in OU. Molecular genetic testing confirmed two heterozygous sequence variations in the BEST1 gene. At 4 years of follow-up, OCT revealed a complete resolution of SRF and a partial resolution of intraretinal hyporeflective spaces in the OD with corresponding improvement in the BCVA to 20/23 Snellen equivalent in the OD, even though outer retinal defects persisted. Our patient denied recent changes in his alimentary habits and medical history at that time. Posteriorly, SRF and intraretinal hyporeflective spaces reappeared in the OD.

CONCLUSION

To the best of our knowledge, this is the first case report of ARB with a transient resolution of retinal edema in one eye without medical treatment and dietary therapy.