New best1 mutations in autosomal recessive bestrophinopathy

Abstract

Purpose: To report the ocular phenotype in patients with autosomal recessive bestrophinopathy and carriers, and to describe novel BEST1 mutations.

Methods: Patients with clinically suspected and subsequently genetically proven autosomal recessive bestrophinopathy underwent full ophthalmic examination and investigation with fundus autofluorescence imaging, spectral domain optical coherence tomography, electroretinography, and electrooculography. Mutation analysis of the BEST1 gene was performed through direct Sanger sequencing.

Results: Five affected patients from four families were identified. Mean age was 16 years (range, 6-42 years). All affected patients presented with reduced visual acuity and bilateral, hyperautofluorescent subretinal yellowish deposits within the posterior pole. Spectral domain optical coherence tomography demonstrated submacular fluid and subretinal vitelliform material in all patients. A cystoid maculopathy was seen in all but one patient. In 1 patient, the location of the vitelliform material was seen to change over a follow-up period of 3 years despite relatively stable vision. Visual acuity and fundus changes were unresponsive to topical and systemic carbonic anhydrase inhibitors and systemic steroids. Carriers had normal ocular examinations including normal fundus autofluorescence. Three novel mutations were detected.

Conclusion: Three novel BEST1 mutations are described, suggesting that many deleterious variants in BEST1 resulting in haploinsufficiency are still unknown. Mutations causing autosomal recessive bestrophinopathy are mostly located outside of the exons that usually harbor vitelliform macular dystrophy-associated dominant mutations.

Fig. 1

Family 1, Patient 1. A 11-year-old otherwise healthy white boy presented with a 6-month history of reduced vision and central scotoma. A. Color fundus photographs demonstrate bilateral, multifocal subretinal yellowish deposits within the posterior pole extending up to the equator. B. There is intense hyperautofluorescence (Topcon TRC-50DX retinal camera; Topcon America, Paramus, NJ) of the yellowish deposits and moderate hyperautofluorescence in the areas of subretinal fluid. C. Spectral domain optical coherence tomography (Topcon 3D-OCT 2000) horizontal scans through the maculae reveal cystoid macular changes and shallow serous macular detachments in both eyes. There is thickening and hyperreflectivity at the inner segment/outer segment photoreceptor junction (“Band 2,” arrows). D. Spectral domain optical coherence tomography horizontal scan through the superior vascular aracade, 3 months after presentation colocalizes the vitelliform material to the subretinal space. The material appears to be emanating from the RPE (stars). E. Genetic screening of the family members confirmed the segregation of the two BEST1 mutations with the disease.

Fig. 2

Family 2, Patient 3. A 6-year-old asymptomatic, U.S.–born African boy was noted to have poor vision by his schoolteacher. A. Color montage fundus photographs. In the right eye, there is subtle vitelliform material nasal to the optic disk. In the left eye, multifocal, curvilinear subretinal yellowish deposits are seen along the superotemporal arcade. B. Fundus autofluorescence imaging (Topcon TRC-50DX retinal camera; Topcon America) demontrates hyperautofluorescence of the vitelliform material in the left eye. C. Enhanced depth imaging spectral domain optical coherence tomography (Heidelberg Spectralis HRA+OCT; Heidelberg Engineering Inc, Heidelberg, Germany) demonstrates bilateral shallow subretinal fluid involving the maculae, a cystoid maculopathy, and subfoveal choroidal thicknesses of 586 μm in the right eye and 482 μm in the left eye. There is thickening and hyperreflectivity at the inner segment/outer segment photoreceptor junction (“Band 2,” arrows). D. The consanguineous parents had normal retinal examinations, 20/20 vision in both eyes and normal quantitative fundus autofluorescence imaging. Two older brothers and one sister, who were not available for genetic screening, were visually asymptomatic with 20/20 vision in both eyes.

Fig. 3

Family 3, Patient 4. A 12-year-old otherwise healthy, emmetropic Puerto Rico-born U.S. boy was noted to have reduced vision on routine eye examination. A. Montage color fundus photographs at initial presentation. There are bilateral, confluent curvilinear subretinal yellowish vitelliform deposits superior to the optic disks, along the temporal vascular arcades and encircling the maculae. B and C. Color fundus photographs 3 years later. The vitelliform material has become more multifocal and dispersed to involve the nasal retinae. Visual acuities remained stable at 20/60 in the right eye and 20/70 in the left eye. D. Fundus autofluorescence imaging (Topcon TRC-50DX retinal camera; Topcon America) demonstrates hyperautofluorescence of the vitelliform material. E. On fluorescein angiography (Topcon TRC-50DX; 61 seconds for the right eye, 92 seconds for the left eye), there is widespread diffuse hyperfluorescence consistent with pooling in the subretinal space and staining of the subretinal yellowish deposits. F. Indocyanine green angiography (Topcon TRC-50DX; 11 minutes 43 seconds for the right eye, 12 minutes 7 seconds for the left eye) demonstrates bilateral midphase hyperfluorescence at the maculae. G. On spectral domain optical coherence tomography (Spectral OCT/SLO; OPKO Instrumentation, Miami, FL), there are bilateral, multifocal serous retinal detachments involving the maculae and cystoid changes in the macula. There is thickening and hyperreflectivity at the inner segment/outer segment photoreceptor junction (“Band 2”, arrows). Subfoveal choroidal thickness measured 537 μm in the right eye and 527 μm in the left eye with enhanced depth imaging.

Fig. 4

Family 4, Patient 5. A 42-year-old woman whose vision problems started at 5 years of age was recently noticing deteriorating central vision. She was the product of a first-cousin marriage. A. Color fundus photographs showing a white–yellow vitelliform lesion at the left fovea. There is RPE and retinal atrophy within the posterior poles. B. Fundus autofluorescence imaging shows bilateral discrete patches of hypoautofluorescence. The vitelliform lesion at the left fovea hyperautofluoresces. C. On spectral domain optical coherence tomography (Heidelberg Spectralis HRA+OCT; Heidelberg Engineering Inc), shallow subretinal fluid is seen at both maculae but not cystoid maculopathy. The subretinal vitelliform deposit is seen in the left eye. Subfoveal choroidal thickness measured 370 μm in both eyes with enhanced depth imaging.

Fig. 5

Analysis of splicing of the BEST1 gene in Patient 5. Complementary DNA from Patient 5, harboring the IVS1+5G>A variant (A, Lane 1), and from a normal control individual (A, Lane 2) was amplified by primers located in Exons 1 and 2 of the BEST1 gene. Amplification of the cDNA of a normal control produced the expected PCR fragment of 234bp (A, Lane 2). This 234bp PCR fragment corresponds to the correctly spliced fragment containing Exons 1 and 2, as shown in the dotted line above in (B). Amplification of the cDNA of the patient homozygous for the IVS1+5G>A variant did not yield the expected PCR product because the first intron (IVS1) was not spliced out, resulting in a large 1538bp PCR product which includes the entire IVS1 (A, Lane 1; B, line below). Lanes 3 and 4 show DNA size standards. cDNA, complementary DNA.