Visualization of Photoreceptors in Birdshot Chorioretinopathy Using Adaptive Optics Scanning Laser Ophthalmoscopy: A Pilot Study

Purpose: Adaptive optics scanning laser ophthalmoscopy (AOSLO) allows en face visualization of specific layers of the retina. This pilot study evaluated the ability of AOSLO to visualize photoreceptor integrity in patients with birdshot chorioretinopathy (BCR).

Method: A total of 16 consecutive patients with HLA-A29+ BCR were imaged using the prototype Apaeros retinal imaging system. Images of high quality were aligned with infrared reflectance photos and correlated with spectral domain optical coherence tomography (SD-OCT).

Results: Images of four eyes of three patients were of sufficient quality to allow posterior pole montage and point-to-point correlation with SD-OCT. Areas of photoreceptor disruption on SD-OCT were seen as patchy areas of loss on AOSLO, whereas areas of intact interdigitation zone and inner segment/outer segment junction correlated with normal appearing photoreceptors on AOSLO.

Conclusions: Using AOSLO, we found one instance of subclinical photoreceptor disruption not seen on SD-OCT. Ultimately, there are unique challenges associated with imaging BCR patients using AOSLO.     

结晶样视网膜色素变性中与CYP4V2基因相关的致病突变

目的：使用Sanger测序法鉴定2个中国结晶样视网膜色素变性(BCD)家系中CYP4V2基因的突变位点。

方法：收集2019-01/09临床诊断为BCD患者的临床相关资料。采集患者、患者家系成员的外周血,提取DNA,利用Sanger测序法鉴定突变位点。

结果：共收集2个BCD先证者,先证者均表现为渐进性视力下降,眼底均可见典型的结晶样物质沉积。测序发现先证者1及其患病的哥哥,妹妹均在CYP4V2基因上存在c.802-8_810del17insGC的纯合突变。而先证者2则在CYP4V2基因上存在c.219T>A(p.F73L)、c.802-8_810del17insGC杂合突变。

结论： 中国BCD患者中最常见的c.802-8_810del17insGC突变在先证者1家系中为纯合突变,是其家系的致病突变。而先证者2则携带了中国BCD患者最常见的c.802-8_810del17insGC杂合突变,同时先证者2还携带c.219T>A(p.F73L)错义突变,突变均影响了CYP4V2基因的正常编码,进而导致疾病。     

Characterization of Bietti crystalline dystrophy patients with CYP4V2 mutations

PURPOSE: Mutations of the CYP4V2 gene, a novel family member of the cytochrome P450 genes on chromosome 4q35, have recently been identified in patients with Bietti crystalline dystrophy (BCD). The aim of this study was to investigate the spectrum of mutations in this gene in BCD patients from Singapore, and to characterize their phenotype. METHODS: Nine patients with BCD from six families were recruited into the study. The 11 exons of the CYP4V2 gene were amplified from genomic DNA of patients by polymerase chain reaction and then sequenced. Detailed characterization of the patients' phenotype was performed with fundal photography, visual field testing, fundal fluorescein angiography, and electroretinography (ERG). RESULTS: Three pathogenic mutations were identified; two mutations, S482X and K386T, were novel and found in three patients. The third mutation, a previously identified 15-bp deletion that included the 3' splice site for exon 7, was found in all nine patients, with six patients carrying the deletion in the homozygous state. Haplotype analysis in patients and controls indicated a founder effect for this deletion mutation in exon 7. Clinical heterogeneity was present in the patients. Compound heterozygotes for the deletion in exon 7 seemed to have more severe disease compared to patients homozygous for the deletion. There was good correlation between clinical stage of disease and ERG changes, but age did not correlate with disease severity. CONCLUSIONS: This study identified novel mutations in the CYP4V2 gene as a cause of BCD. A high carrier frequency for the 15-bp deletion in exon 7 may exist in the Singapore population. Phenotype characterization showed clinical heterogeneity, and age did not correlate with disease severity.     

A Novel Compound Heterozygous Mutation in the CYP4V2 Gene in a Japanese Patient with Bietti's Crystalline Corneoretinal Dystrophy

Purpose: To describe the clinical and genetic characteristics of a Japanese family in which one member exhibited Bietti's crystalline corneoretinal dystrophy (BCD). Methods: Using direct sequencing, mutation screening was performed in the CYP4V2 gene of both the patient with BCD and her daughter. Ophthalmic examinations were performed to determine the clinical features of both subjects. Results: The 64-year-old female patient had a bilateral visual acuity of 0.4. Slit lamp examination revealed bilateral crystalline-like deposits at the superior limbus of the cornea. Fundus examination revealed there was chorioretinal atrophy along with numerous glistening yellowish-white crystalline deposits that were scattered throughout the posterior pole and the mid-peripheral retina. Standard flash electroretinography showed an extinguished electroretinogram and Goldmann kinetic perimetry detected a relative scotoma. Genetic analysis revealed that the patient had a heterozygous mutation in the CYP4V2 gene (IVS6-8delTCATACAGGTCATCGCG/GC), which is the most commonly found mutation in Japanese patients with BCD. Furthermore, the patient was also shown to have a novel heterozygous point mutation in exon 9 of the CYP4V2 gene (c.1168C>T). In contrast, her daughter exhibited no clinical findings for BCD even though she carried the same heterozygous mutation in the CYP4V2 gene (c.1168C>T). Conclusion: A novel compound heterozygous mutation was found in the CYP4V2 gene of a patient with BCD. This previously unreported c.1168C>T mutation causes a missense mutation (p.R390C) in the CYP4V2 protein.     

Novel CYP4V2 mutations associated with Bietti crystalline corneoretinal dystrophy in Chinese patients

AIM: To analyze the CYP4V2 mutations in five unrelated Chinese patients with Bietti crystalline corneoretinal dystrophy (BCD) and to provide clinical features of these patients. BCD is a rare monogenic autosomal recessively inherited disorder characterized by the presence of crystals in the retina and retinal pigment epithelium atrophy. Mutations in the CYP4V2 gene have been found to be causative for BCD.METHODS:Ophthalmic examinations were carried out in the affected individuals. Peripheral blood samples were collected and genomic DNA was extracted. All exons and flanking intronic regions of the CYP4V2 gene were amplified with polymerase chain reaction and screened for mutations by direct DNA sequencing. One hundred control chromosomes were also screened to exclude nonpathogenic polymorphisms.RESULTS: Fundus examination revealed the presence of tiny yellowish-sparkling crystals at the posterior pole of the fundus and atrophy of the retinal pigment epithelium in all patients. Choroid neovascularization was noted in one patient. Five different CYP4V2 mutations were identified, including two missense mutations (p.F73L, p.R400H), two splice site mutations (c.802-8_810del17insGC, c.1091-2A>G), and one single base-pair deletion (p.T479TfsX7 or c.1437delC). The two splice site mutations were identified in three of the patients with BCD. Mutation p.T479TfsX7 was a novel mutation not observed in any of 100 ethnically matched control chromosomes.CONCLUSION: Mutation c.802-8_810del17insGC and c.1091-2A>G are common mutations in Chinese patients with BCD. Our results expand the allelic heterogeneity of BCD.     

A novel mutation of CYP4V2 gene associated with Bietti crystalline dystrophy complicated by choroidal neovascularization

AIM: To investigate the clinical characteristics and genetic features of a Bietti crystalline dystrophy (BCD) proband in a Chinese family. METHODS: A Chinese female diagnosed with BCD complicated by bilateral choroidal neovascularization (CNV) and her parents underwent complete ophthalmic examinations, including fundus autofluorescence (AF), fundus photography (FP), fundus fluorescein angiography (FFA), visual field testing, full-field electroretinography (ERG), optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). The sequencing of the CYP4V2 gene was performed to the whole family. RESULTS: Bilateral tiny glittering crystal-like deposits and differing extent of atrophy of the retinal pigment epithelium (RPE) were found in the posterior pole of her fundus. The diffuse hypo-fluorescence shown on AF images and window defects shown on FFA both indicated the atrophy of the RPE and choriocapillaris. OCT showed the thinning of the RPE and choriocapillaris layer, ellipsoid zone (EZ) band defect and CNV in both eyes. OCTA images proofed bilateral type 2 CNV. The visual field test showed central and paracentral scotoma. ERG showed a slightly decreased b-wave in scotopic ERG. Gene sequencing identified three mutations of the CYP4V2 gene, c.802_807del, c.810delT, and c.1388G>A. The mutation c.1388G>A was a novel substitution mutation. CONCLUSION: The novel mutation c.1388G>A may be a possible cause that could induce the clinical phenotype of BCD.     

携带CYP4V2基因突变的结晶样视网膜色素变性患者的表型特征

目的 分析国人结晶样视网膜色素变性（BCD）患者CYP4V2基因型及表型特征。设计 回顾性病例系列。研究对象 北京同仁医院结晶样视网膜色素变性患者138例。方法 回顾患者病历记录及眼科检查结果。先证者、直系亲属及家系患病成员采集外周静脉血,Sanger测序及实时定量荧光PCR检测先证者CYP4V2基因突变,并对致病性突变进行家系共分离验证。主要指标 最佳矫正视力、眼前节及眼底情况、CYP4V2基因突变。结果 138例BCD患者均携带CYP4V2基因双突变,突变c.802-810del17insCG、c.1091-2A>G和p.H331P是本组患者的常见突变。患者平均最佳矫正视力（LogMAR）（1.17±0.95）,平均发病年龄（29.19±9.64）岁,视力损伤程度与病程相关,不受发病年龄影响。所有患者眼底均可见细小颗粒状黄白色结晶沉积,结晶沉积范围及密度随病程而加重。结论 本研究拓展了BCD致病基因CYP4V2突变谱,BCD患者临床特征明显,结合多种影像学检查方法可有效进行诊断,致病基因突变的确定可为患者提供相应的遗传咨询帮助。（眼科, 2020, 29： 93-97）     

Detailed functional and structural phenotype of Bietti crystalline dystrophy associated with mutations in CYP4V2 complicated by choroidal neovascularization

Purpose: To describe in detail the phenotype of a patient with Bietti crystalline dystrophy (BCD) complicated by choroidal neovascularization (CNV) and the response to intravitreal Bevacizumab (Avastin^®; Genentech/Roche).

Methods: A 34-year-old woman with BCD and mutations in CYP4V2 (c.802-8_806del13/p.H331P:c992A>C) underwent a complete ophthalmic examination, full-field flash electroretinography (ERG), kinetic and two-color dark-adapted perimetry, and dark-adaptometry. Imaging was performed with spectral domain optical coherence tomography (SD-OCT), near infrared (NIR) and short wavelength (SW) fundus autofluorescence (FAF), and fluorescein angiography (FA).

Results: Best-corrected visual acuity (BCVA) was 20/20 and 20/60 for the right and left eye, respectively. There were corneal paralimbal crystal-like deposits. Kinetic fields were normal in the peripheral extent. Retinal crystals were most obvious on NIR-reflectance and corresponded with hyperreflectivities within the RPE on SD-OCT. There was parafoveal/perifoveal hypofluorescence on SW-FAF and NIR-FAF. Rod > cone sensitivity loss surrounded fixation and extended to ~10° of eccentricity corresponding to regions of photoreceptor outer segment-retinal pigmented epithelium (RPE) interdigitation abnormalities. The outer nuclear layer was normal in thickness. Recovery of sensitivity following a ~76% rhodopsin bleach was normal. ERGs were normal. A subretinal hemorrhage in the left eye co-localized with elevation of the RPE on SD-OCT and leakage on FA, suggestive of CNV. Three monthly intravitreal injections of Bevacizumab led to restoration of BCVA to baseline (20/25).

Conclusion: crystals in BCD were predominantly located within the RPE. Photoreceptor outer segment and apical RPE abnormalities underlie the relatively extensive retinal dysfunction observed in relatively early-stage BCD. Intravitreal Bevacizumab was effective in treating CNV in this setting.     

Crystal deposits on the lens capsules in Bietti crystalline corneoretinal dystrophy associated with a mutation in the CYP4V2 gene

Purpose: We report a patient (Case 1) with Bietti crystalline corneoretinal dystrophy (BCD) associated with previously unknown findings of crystal‐like deposits on the anterior and posterior lens capsules. This patient is one of four (Cases 1–4) in whom we have found BCD associated with the same mutation in the CYP4V2 gene. Methods: We present a case report with molecular diagnosis. A 45‐year‐old man (Case 1) was referred to our clinic with complaints of gradual progression of visual disturbances and night blindness. His visual acuity was limited to hand movement bilaterally. Slit‐lamp biomicroscopy disclosed glistening, crystal‐like deposits on the anterior and posterior lens capsules, as well as on the corneal stroma near the corneoscleral limbus. No such deposit was found in the lens stroma. Fundus examination disclosed profound chorioretinal atrophy with scarce crystal deposits. Full‐field electroretinography showed extinguished responses of isolated rods, isolated cones, and mixed rods and cones. Results: Molecular genetic analysis revealed that the subject had a homozygous mutation in the CYP4V2 gene (IVS6–8delTCATACAGGTCATCGCG/insGC), which is most commonly found in Japanese patients with BCD. Three other cases (Cases 2–4) of BCD associated with the same mutation did not show such crystal‐like deposits on the lens surface. Conclusions: Although their exact origin remains unknown, crystal‐like deposits may appear on the lens capsule of patients with BCD associated with a mutation in the CYP4V2 gene.     

Variant Phenotype of Best Vitelliform Macular Dystrophy Associated with Compound Heterozygous Mutations in VMD2

Purpose: To characterize the phenotype of members of a Swedish family with Best macular dystrophy and two distinct mutations in VMD2. Methods: Venous blood samples were obtained from six family members and screened for mutations in VMD2. Six individuals were examined clinically, four of whom were further investigated with full-field electroretinography (ERG), electro-oculography (EOG), multifocal electroretinography (mfERG), and optical coherence tomography (OCT). Results: The VMD2 mutations resulting in Arg141His and Tyr29stop were identified in family members. Two individuals harbored both mutations, one mutation in each VMD2 allele. These two family members had an abnormal EOG and their full-field ERG demonstrated widespread degeneration with a prolonged implicit time in the cone 30-Hz flicker ERG. MfERG verified reduction of the central retinal function and OCT demonstrated intraretinal fluid, swelling, and thickening of the outer retina-RPE-choroid complex (ORCC). Conclusion: A previously undescribed severe form of Best macular dystrophy is associated with compound heterozygous mutations in VMD2.     

Optical coherence tomographic findings of crystal deposits in the lens and cornea in Bietti crystalline corneoretinopathy associated with mutation in the CYP4V2 gene

Background

We report the optical coherence tomography (OCT) findings of crystalline deposits in the cornea and lens of a patient with Bietti crystalline dystrophy (BCD), thus providing evidence for a better understanding of the pathophysiology of BCD.

Patient

A 49-year-old man showing typical chorioretinal degeneration with a CYP4V2 mutation was diagnosed with BCD.

Observations

The anterior segment OCT images clearly showed flat hyperreflective plaques just beneath the corneal epithelium and in the lens epithelium. The crystals were not located on the outer surface of the lens capsule as previously described but on the inner surface of the anterior capsule.

Conclusions

This finding suggests that the crystals in the lens of patients with BCD may be produced in the same way as corneal or retinal crystalline deposits and therefore result from a systemic abnormality of lipid metabolism rather than by previously considered possibilities, such as release from the retina adhering to the lens capsule.     

Fuchs Endothelial Corneal Dystrophy in a Heterozygous Carrier of Congenital Hereditary Endothelial Dystrophy Type 2 with a Novel Mutation in SLC4A11

Purpose: Congenital hereditary endothelial dystrophy (CHED) is a rare genetic disorder caused by mutations in corneal endothelial cells. CHED can be divided into 2 types by the modes of inheritance; CHED type 1 (CHED1) with autosomal dominant inheritance and CHED type 2 (CHED2) with autosomal recessive inheritance. Mutations in the sodium bicarbonate transporter-like solute carrier family 4 member 11 (SLC4A11) gene result CHED2.

Methods: A 37 years old female was clinically diagnosed as CHED2. Peripheral blood from the patient and her family members was obtained under informed consents. Genomic DNA was extracted in their WBCs, and whole exons and exon-intron boundaries of the SLC4A11 gene were amplified using polymerase chain reaction. The amplified materials were analyzed by direct sequencing method.

Results: The sequencing results of the SLC4A11 gene showed a novel homozygous mutation in exon 9 (c.1158C?>?A, p.C386*) in the proband with CHED2 phenotype. Her father and sister showing normal cornea were heterozygous carriers of the mutation. Her mother showing late onset Fuchs endothelial corneal dystrophy (FECD) also had the same mutation heterozygously.

Discussion: We report a novel nonsense mutation of the SLC4A11 gene in the patient with CHED2. In addition, one of heterozygous carriers in this family showed features of late onset FECD. Close clinical ocular examination for the heterozygous carriers should be performed to detect late onset FECD.