Genotype and Long-term Clinical Course of Bietti Crystalline Dystrophy in Korean and Japanese Patients

Enhanced genotype-phenotype analysis using multimodal adaptive optics and 3D protein structure in Bietti Crystalline Dystrophy

Purpose

Deep phenotyping of genetic retinal disease using multimodal adaptive optics ophthalmoscopy and protein structure variant analysis.

Observations

In a patient with extensive atrophy of the retinal pigment epithelium and yellow deposits in the retina, genetic testing identified two CYP4V2 variants: c.802-8_810delinsGC and c.1169G > A, p.Arg390His. AI-generated protein structures indicated loss of CYP4V2 function. Reflectance confocal and multiple-scattering Adaptive Optics Scanning Light Ophthalmoscopy (AOSLO) captured crystalline deposits throughout the retina as well as previously unreported cyst-like structures that were mainly independent from the crystalline deposits. Sequential AOSLO imaging was conducted and revealed anatomical and morphological changes in the cysts and surrounding cellular structures.

Conclusions and importance

Cyst-like changes may represent a new BCD degenerative feature. Characterizing retinal genetic disease variants with protein structural modeling and phenotyping with AOSLO represents an advanced approach for clinical diagnosis and may serve as a biomarker of disease progression.

Clinical Exome-Based Redefinition and Reclassification of Retinitis Pigmentosa

BACKGROUND

Because of the low prevalence of inherited retinal diseases, reports on the distribution of retinitis pigmentosa (RP)-related genes in Korean patients are scarce. The aim of this study was to determine the mutation spectrum and allele frequency and observe the final diagnoses in a Korean cohort clinically diagnosed with RP.

METHODS

We used whole-exome sequencing (WES) to analyze a Korean cohort of 100 unrelated patients clinically diagnosed with RP. The possible pathogenicity of each variant was assessed based on the guidelines of the American College of Medical Genetics and Genomics and Association for Molecular Pathology, in-silico prediction tools, known clinical phenotypes, and inheritance patterns.

RESULTS

Definite causative genes were detected in 60/100 patients (60.0%). Of these 60 cases, USH2A was the most common causative gene (14/60, 23.3%), followed by EYS (13/60, 21.7%) and RP1 (6/60, 10.0%). The clinical diagnosis was redefined in 9 of the 60 probands (15.0%) with causative genes after WES. Five of the 60 patients (8.3%) carried a causative variant in CHM, and the clinical diagnosis was redefined as choroideremia. Leber congenital amaurosis was diagnosed in 2/60 probands (3.3%), and RDH12 and RPGRIP1 were the causative genes in each patient. One patient (1/60, 1.7%) was diagnosed with Bietti's crystalline dystrophy, with CYP4V2 identified as the causative gene. In another patient (1/60, 1.7%), ABCA4 variants were detected with clinical findings suggestive of cone-rod dystrophy.

CONCLUSION

This study reports the mutational spectrum of a cohort of Korean patients with a clinical diagnosis of RP who were referred for genetic testing. This study adds valuable data regarding the frequency of genes as well as their relation to the age of symptom onset and relation to other inherited retinal degenerations.

Natural history of progressive vision loss in Bietti crystalline dystrophy: a model-based meta-analysis

PURPOSE

Bietti crystalline corneoretinal dystrophy (BCD) is an autosomal recessive progressive retinal degenerative disease due to mutations in the CYP4V2 gene. Best-corrected visual acuity (BCVA) is a common primary endpoint in clinical trials for retinal diseases, but the natural history of BCVA loss remains unclear because of the heterogeneity of manifestations in BCD patients.

METHODS

Based on the individual data of untreated BCD patients, a disease progression model was established using the change in BCVA from baseline as an index, and covariates including age of onset, age, duration of disease, baseline BCVA, gender, race (East Asian/non-East Asian), genotype, and family history. Then, based on the final model, the natural disease progression characteristics of BCD were simulated.

RESULT

A total of 14 studies met the inclusion criteria, with a total sample size of 117 cases, including 6 studies (N=80) with East Asian populations and 9 studies (N=37) with non-East Asian populations. The change of BCVA from baseline increased linearly with time, and the disease progression model of BCD was successfully established. BCVA increased by 0.06 logarithm of the minimum angle of resolution (LogMAR) per year in BCD patients. BCVA increased by 0.09 LogMAR per year in patients with BCVA≥0.5LogMAR and disease duration more than 10 years.

CONCLUSIONS

For the first time, we successfully established a BCD disease progression model based on the change in BCVA from baseline. The mean visual acuity loss increased linearly with the progression of the disease. A sharper loss of BCVA may be expected in patients with BCVA≥0.5LogMAR and disease duration ≥10 years.

A 30-year-old man with Bietti crystalline dystrophy:a rare case report from Syria

Introduction

Bietti crystalline dystrophy (BCD) is a rare, inherited eye disease that causes progressive damage to the back of the eye (chorioretinal atrophy), characterized by sparkling crystals in the cornea and retina.

Case presention

A 30-year-old man presented with gradual vision loss in both eyes. Fundus photography revealed retinal crystals and retinal pigment epithelium atrophy, consistent with BCD. Enhanced depth imaging optical coherence tomography confirmed retinal and choroidal abnormalities, supporting the diagnosis. Genetic testing was not performed due to financial constraints.

Clinical discussion

Subretinal rAAV2/8-hCYP4V2 gene therapy for BCD is safe and effective, but COVID-19 or AAV8 antibodies may hinder its efficacy. VFQ-25 correlates with visual acuity improvement. Hypertriglyceridemia and hypercholesterolemia were observed as potential side effects.

Conclusion

Health care professionals should be vigilant in recognizing rare eye diseases like BCD, even in uncommon regions. Further research is crucial to understand BCD, develop treatments, and improve the quality of life for affected individuals.

Quantitative swept-source optical coherence tomography angiography (SS-OCTA) analysis of macular microvascular alterations in Bietti crystalline dystrophy

PURPOSE

Bietti crystalline dystrophy (BCD) is a rare retinal dystrophy characterized by progressive visual impairment. This study aimed to evaluate changes in retinal and choroidal vessels and blood flow in BCD patients using swept-source optical coherence tomography angiography (SS-OCTA) and to investigate potential parameters associated with visual function.

METHODS

This cross-sectional study included 166 eyes from 86 clinically diagnosed BCD patients, classified into three disease stages based on Yuzawa's classification. OCTA imaging (VG200S; SVision Imaging, Henan, China) covered a 12 mm × 12 mm area of the macula, measuring thickness, vessel density (VD), perfusion area (PA), choroidal vascularity index (CVI), choroidal vascularity volume (CVV), and foveal avascular zone (FAZ) metrics. Associations between OCTA parameters and visual function metrics, including best-corrected visual acuity (BCVA), mean deviation (MD) and visual field index (VFI) of the Humphrey visual field test, were analyzed.

RESULTS

By stage 3, 92 % of eyes exhibited an undetectable ellipsoid zone (EZ). From stage 1 to stage 2, VD in all retinal layers decreased significantly (P < 0.05), whereas differences between stages 2 and 3 were not statistically significant (P > 0.05). The FAZ area and perimeter showed no significant difference across the three stages (P > 0.05). Choroidal parameters, including PA, CVI, and CVV, progressively decreased across all stages (P < 0.001). Multivariate regression analysis revealed that SVC-VD (P < 0.001), SVC-PA (P < 0.001) and choroid-PA (P = 0.030) were significantly associated with BCVA, while DVC-VD (P = 0.014), outer retinal thickness (P = 0.011), and CVI (P = 0.004) were significantly associated with visual field damage.

CONCLUSIONS

SS-OCTA effectively quantifies the progressive microvascular changes in the retina and choroid associated with BCD. Retinal vascular alterations are prominent in the early stages of the disease, whereas choroidal damage persists throughout its progression. OCTA parameters of the retina and choroid demonstrate varying degrees of correlation with visual function, underscoring their potential as biomarkers for monitoring disease progression and evaluating therapeutic efficacy.

Safety and Vision Outcomes Following Gene Therapy for Bietti Crystalline Dystrophy: A Nonrandomized Clinical Trial

Importance

Bietti crystalline dystrophy (BCD) is a severe genetic retinopathy caused by variants in the CYP4V2 gene. Currently, there is no approved treatment for BCD.

Objective

To evaluate safety and vision outcomes following gene therapy with adeno-associated virus (AAV) encoding CYP4V2 (rAAV-hCYP4V2, NGGT001 [Next Generation Gene Therapeutics]).

Design, Setting, and Participants

This open-label, dose-escalation nonrandomized clinical trial was conducted from February 2023 to May 2024 at 2 study sites in China. Patients with genetically confirmed biallelic disease-linked CYP4V2 variants received subretinal injections of rAAV2-hCYP4V2 at 1 of 2 dosage levels and were followed up for 12 months.

Intervention

A single unilateral injection of 1.5 × 1011 or 3.0 × 1011 total vector genomes of recombinant AAV-hCYP4V2 in the worse eye, based on visual acuity letter score.

Main Outcomes and Measures

The primary outcome was safety, assessed by clinical examination of ocular inflammation and evaluated by routine clinical chemistry and immunogenicity testing. Secondary outcomes were changes in visual function from baseline in best-corrected visual acuity (BCVA), microperimetry, and contrast sensitivity 12 months after treatment.

Results

Among 12 patients with BCD (6 patients per dose group), mean (SD) patient age was 40.5 (7.1) years, and 5 patients (42%) were female. No severe adverse events related to the treatment were observed. However, mild intraocular inflammation was noted in 1 participant. The median (IQR) baseline BCVA letter score for the study eye was 34 (10-53), equivalent to 20/200 Snellen, while the nonstudy eye had a median (IQR) BCVA of 60 (40-67), equivalent to approximately 20/63 Snellen. At 12 months, the study eye improved by a mean (SD) letter score of 13.9 (13.1) compared with 6.3 (7.4) in the nonstudy eye. The 12-month median (IQR) BCVA for the study eye was 53 (37-64) (equivalent to approximately 20/80 Snellen) and 62 (42-70) (approximately 20/50 Snellen) for the nonstudy eye.

Conclusions and Relevance

This open-label, exploratory nonrandomized clinical trial identified no serious safety concerns related to gene therapy over 12 months' follow-up among patients with BCD. While improvement in BCVA was noted, the magnitude was within test-retest values typically noted in eyes with very low levels of visual acuity, and BCVA improvement in both the study and nonstudy eyes could be related to a learning effect, with greater improvement in the study eye possibly related to study eyes' being the worse-seeing eye.

Trial Registration

ClinicalTrials.gov Identifier: NCT06302608.

Investigating Microperimetric Features in Bietti Crystalline Dystrophy Patients: A Cross-Sectional Longitudinal Study in a Large Cohort

Purpose

To assess the clinical and genetic characteristics of patients with Bietti crystalline dystrophy (BCD) with a focus on potential of microperimetry in monitoring macular function.

Methods

A total of 208 genetically-confirmed BCD patients were enrolled in this retrospective study. The patients were categorized into subgroups based on their fundus characteristics (fovea sparing and fovea involved), optical coherence tomography (OCT) findings (presence/absence of retinal pigment epithelium [RPE] or ellipsoid zone [EZ] line at the fovea/parafovea), and genetic profiles (Mis/Mis, Tru/Mis, Tru/Tru). Fixation patterns were analyzed, and macular sensitivity (MS) parameters were compared among different groups. Longitudinal analysis was performed to calculate the annual changes in MS parameters. Correlation between genotype and phenotype were further investigated by analyzing cumulative incidence of vision impairment among different genotypic groups.

Results

Patients with well-preserved RPE or EZ at the foveal/parafoveal region exhibited higher MS. Notably, there was a decline in sensitivity parameters, with a decrease of -2.193 dB/year (95% confidence interval [CI] -4.292 to -0.095, P = 0.041) at the fovea and -1.353 dB/year (95% CI -2.047 to -0.659, P < 0.001) in average sensitivity. An age-adjusted comparison of sensitivity among genotypic groups and cumulative incidence analyses showed no association between genotypic groups and vision loss.

Conclusions

Microperimetry proves to be one of a credible tool for detecting macular functional changes in BCD patients. BCD patients with different genotypes may have similar disease progression.

DISCREPANCY BETWEEN FUNDUS AUTOFLUORESCENCE ABNORMALITY AND VISUAL FIELD LOSS IN BIETTI CRYSTALLINE DYSTROPHY

PURPOSE

The aim of this study was to explore the potential benefits of retinal pigment epithelium replacement therapy in patients with Bietti crystalline dystrophy (BCD) by assessing the disease pathology with the distinctive relationship between fundus autofluorescence (FAF) abnormality and visual field defect.

METHODS

Sixteen eyes from 16 patients with BCD and 16 eyes from 16 patients with RHO-associated retinitis pigmentosa were included. Fundus autofluorescence, optical coherence tomography, and Goldmann perimetry results were retrospectively reviewed and assessed using image analyses.

RESULTS

In patients with BCD, the FAF abnormality area was not correlated with the overall visual field defect area and median overall visual field defect area (57.5%) was smaller than FAF abnormality area (98.5%). By contrast, the ellipsoid zone width was significantly correlated with the central visual field area (r = 0.806, P < 0.001). In patients with RHO-associated retinitis pigmentosa, the FAF abnormality area and ellipsoid zone width were significantly correlated with the overall visual field defect area (r = 0.833, P < 0.001) and central visual field area (r = 0.887, P < 0.001), respectively.

CONCLUSION

The FAF abnormality shown in patients with BCD involves retinal pigment epithelium degeneration without complete loss of photoreceptors or visual function. These results suggest that patients with BCD are good candidates for retinal pigment epithelium replacement therapy for preservation of residual visual function.

Bietti's crystalline dystrophy: genotyping and deep qualitative and quantitative phenotyping in preparation for clinical trials

PURPOSE

To qualitatively and quantitatively characterise the genotypes and phenotypes of Bietti's crystalline dystrophy (BCD) in a cohort of patients.

DESIGN

Cross-sectional and observational study.

METHODS

Clinically confirmed BCD patients were recruited for genotyping and phenotyping. Multiple retinal imaging modalities were employed. Atrophy in the fovea was adopted as major consideration for staging strategy, while percentage area of autofluorescence (AF) atrophy (PAFA) in the macula was determined for quantitation.

RESULTS

In 74 clinically diagnosed BCD patients, c.802-8_810del17insGC was shown the predominant variant of the CYP4V2 gene (allele frequency 55.4%). Sixty-two cases (123 eyes) with full imaging data were classified according to a modified criterion into stages 1 (n=8, 6.50%), 2A (n=9, 7.32%), 2B (n=17, 13.82%), 3A (n=30, 24.39%) and 3B (n=59, 47.97%). The eyes of the stage 2B were particularly deemed 'high risk' due to atrophy near fovea, while in stage 3A, though with remarkable foveal atrophy, preserved retinal pigment epithelium/photoreceptor islands near the fovea were found in 14 eyes. A tendency of increase in PAFA with age was found (rs=0.31, p=0.014). Significant PAFA increase was shown through stages 1 to 3B, and best-corrected visual acuity (BCVA, Logarithm of the Minimum Angle of Resolution) was shown to moderately correlate with PAFA (rs=0.56, p<0.001).

CONCLUSION

The PAFA might be an efficient biomarker for BCD severities correlating with BCVA. The highly heterogeneous chorioretinopathy and BCVA of BCD cases appear to be associated with disease stages, progression types and patients' ages. Foveal involvement should be of a major concern for consideration of potential therapeutic intervention.

Specification of variant interpretation guidelines for inherited retinal dystrophy in Japan

Accurate interpretation of sequence variants in inherited retinal dystrophy (IRD) is vital given the significant genetic heterogeneity observed in this disorder. To achieve consistent and accurate diagnoses, establishment of standardized guidelines for variant interpretation is essential. The American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines for variant interpretation serve as the global "cross-disease" standard for classifying variants in Mendelian hereditary disorders. These guidelines propose a systematic approach for categorizing variants into 5 classes based on various types of evidence, such as population data, computational data, functional data, and segregation data. However, for clinical genetic diagnosis and to ensure standardized diagnosis and treatment criteria, additional specifications based on features associated with each disorder are necessary. In this context, we present a comprehensive framework outlining the newly specified ACMG/AMP rules tailored explicitly to IRD in the Japanese population on behalf of the Research Group on Rare and Intractable Diseases (Ministry of Health, Labour and Welfare of Japan). These guidelines consider disease frequencies, allele frequencies, and both the phenotypic and the genotypic characteristics unique to IRD in the Japanese population. Adjustments and modifications have been incorporated to reflect the specific requirements of the population. By incorporating these IRD-specific factors and refining the existing ACMG/AMP guidelines, we aim to enhance the accuracy and consistency of variant interpretation in IRD cases, particularly in the Japanese population. These guidelines serve as a valuable resource for ophthalmologists and clinical geneticists involved in the diagnosis and treatment of IRD, providing them with a standardized framework to assess and classify genetic variants.

Gene replacement therapy in Bietti crystalline corneoretinal dystrophy: an open-label, single-arm, exploratory trial

Bietti crystalline corneoretinal dystrophy is an inherited retinal disease caused by mutations in CYP4V2, which results in blindness in the working-age population, and there is currently no available treatment. Here, we report the results of the first-in-human clinical trial (NCT04722107) of gene therapy for Bietti crystalline corneoretinal dystrophy, including 12 participants who were followed up for 180-365 days. This open-label, single-arm exploratory trial aimed to assess the safety and efficacy of a recombinant adeno-associated-virus-serotype-2/8 vector encoding the human CYP4V2 protein (rAAV2/8-hCYP4V2). Participants received a single unilateral subretinal injection of 7.5 × 1010 vector genomes of rAAV2/8-hCYP4V2. Overall, 73 treatment-emergent adverse events were reported, with the majority (98.6%) being of mild or moderate intensity and considered to be procedure- or corticosteroid-related; no treatment-related serious adverse events or local/systemic immune toxicities were observed. Compared with that measured at baseline, 77.8% of the treated eyes showed improvement in best-corrected visual acuity (BCVA) on day 180, with a mean ± standard deviation increase of 9.0 ± 10.8 letters in the 9 eyes analyzed (p = 0.021). By day 365, 80% of the treated eyes showed an increase in BCVA, with a mean increase of 11.0 ± 10.6 letters in the 5 eyes assessed (p = 0.125). Importantly, the patients' improvement observed using multifocal electroretinogram, microperimetry, and Visual Function Questionnaire-25 further supported the beneficial effects of the treatment. We conclude that the favorable safety profile and visual improvements identified in this trial encourage the continued development of rAAV2/8-hCYP4V2 (named ZVS101e).

Longitudinal structure-function analysis of molecularly-confirmed CYP4V2 Bietti Crystalline Dystrophy

OBJECTIVES

Bietti Crystalline Dystrophy (BCD) is an autosomal recessive progressive retinal disease caused by mutations in CYP4V2. We have characterised the natural history including structural and functional measures to identify potential outcome metrics for future clinical trials.

METHODS

Molecularly-confirmed BCD patients with biallelic variants in CYP4V2 were retrospectively identified from Moorfields Eye Hospital (UK). Clinical details including results of molecular genetic testing, best-corrected visual acuity (BCVA) and spectral-domain optical coherence tomography (OCT) scans were extracted. From OCT scans, ellipsoid zone (EZ) measures, foveal thickness of the whole retina, outer retina and choroid were measured. Age-related changes of clinical parameters were assessed with linear mixed models.

RESULTS

Twenty-eight BCD patients were identified, with median age at baseline of 37 years (interquartile range [IQR]: 30-49.5). Median follow-up was 7.7 years (IQR: 3.4-14.5). Most patients (41.7%) showed chorioretinal atrophy at baseline. All OCT parameters showed significant age-related loss (p < 0.05), with EZ measures and choroidal thickness displaying the most rapid degeneration (2.3-3.3% per year vs 0.6-1.5% per year). Median BCVA was 0.2 LogMAR (IQR: 0-0.5) at baseline and showed small age-related loss ( + 0.016 LogMAR per year, p = 0.0019). Patients exhibited substantial phenotypic variability.

CONCLUSIONS

BCD presents between age 25 and 40, and slowly progresses to an advanced chorioretinal atrophy and vision loss by age 60. BCVA may be preserved until late, and is seemingly poorly representative of disease progression. OCT parameters capturing EZ and choroid changes may afford more suitable trial outcome measures.

Longitudinal Natural History Study of Visual Function in Bietti Crystalline Dystrophy: Implications for Early Intervention

Purpose

To delineate the natural history of visual function parameters over time in individuals with Bietti crystalline dystrophy.

Methods

This was a single-center retrospective longitudinal cohort study. Participants (n = 29) with a clinical diagnosis of Bietti crystalline dystrophy who harbored two alleles of disease-causing variants of the cytochrome P450 family 4 subfamily V member 2 gene (CYP4V2) were enrolled. Best-corrected visual acuity (BCVA), visual field (VF), and full-field ERG (ffERG) at baseline and their changes during the follow-up period were evaluated. Annual progression rates were calculated using three methods.

Results

The mean age at the initial visit was 34.2 ± 7.5 years, with 5.9 ± 3.1 years follow-up. The annual progression rate from the longitudinal analysis using averaged individual progression rates was 0.079 logMAR units for BCVA, 1.14 dB for mean defect (MD) value of VF, and -18.06 µV and -5.45 µV for the b-wave amplitudes of scotopic 3.0 ERG and photopic 3.0 ERG, respectively. Mixed-model linear regression revealed annual progression rates of 0.068 logMAR units, 0.86 dB, -13.29 µV, and -3.75 µV, respectively. Cross-sectional progression rates from visual function versus age at baseline were 0.011 logMAR units, 0.47 dB, -1.85 µV, and -1.07 µV, respectively, which were significantly slower than those from the longitudinal data. Interocular symmetries for the MD values of VF and ffERG were good.

Conclusions

Annual BCVA, VF, and ffERG progression rates were rapid, emphasizing the need for regular follow-up and early intervention. The progression rate cannot be inferred accurately from cross-sectional data from patients of different ages.

An In-Depth Single-Gene Worldwide Carrier Frequency and Genetic Prevalence Analysis of CYP4V2 as the Cause of Bietti Crystalline Dystrophy

Conclusions

Our analysis estimates BCD prevalence and revealed large differences among various populations. Moreover, it highlights advantages and limitations of the gnomAD database.

Methods

CYP4V2 gnomAD data and reported mutations were used to calculate carrier frequency of each variant. An evolutionary-based sliding window analysis was used to detect conserved protein regions. Potential exonic splicing enhancers (ESEs) were identified using ESEfinder.

Purpose

Bietti crystalline dystrophy (BCD) is a rare monogenic autosomal recessive (AR) chorioretinal degenerative disease caused by biallelic mutations in CYP4V2. The aim of the current study was to perform an in-depth calculation of worldwide carrier frequency and genetic prevalence of BCD using gnomAD data and comprehensive literature CYP4V2 analysis.

Results

We identified 1171 CYP4V2 variants, 156 of which were considered pathogenic, including 108 reported in patients with BCD. Carrier frequency and genetic prevalence calculations confirmed that BCD is more common in the East Asian population, with ∼19 million healthy carriers and 52,000 individuals who carry biallelic CYP4V2 mutations and are expected to be affected. Additionally, we generated BCD prevalence estimates of other populations, including African, European, Finnish, Latino, and South Asian. Worldwide, the estimated overall carrier frequency of CYP4V2 mutation is 1:210, and therefore, ∼37 million individuals are expected to be healthy carriers of a CYP4V2 mutation. The estimated genetic prevalence of BCD is about 1:116,000, and we predict that ∼67,000 individuals are affected with BCD worldwide.

Translational Relevance

This analysis is likely to have important implications for genetic counseling in each studied population and for developing clinical trials for potential BCD treatments.

PREDICTED PROTEIN STRUCTURE VARIATIONS INDICATE THE CLINICAL PRESENTATION OF CYP4V2-RELATED BIETTI CRYSTALLINE DYSTROPHY

PURPOSE

To investigate the relationship between different CYP4V2 disease-causing variants and disease severity in Bietti crystalline dystrophy (BCD).

METHODS

Twenty-one subjects from 19 unrelated families with a clinical diagnosis of BCD were enrolled. A novel severity prediction score for BCD based on the predicted molecular impact of CYP4V2 variants was applied for grouping and subsequent analyses. The more severe variants led to less CYP4V2 protein function preservation and a higher severity prediction score.

RESULTS

All subjects harbored two alleles of CYP4V2 disease-causing variants, of which c.802-8_810del17insGC was the most prevalent (14/21, 66.67%) and c.1507G>C was novel. According to the severity score, the subjects were categorized into severe, moderate, and mild groups with different preservation of central vision (mean logMAR visual acuity 0.95 ± 0.82, 0.89 ± 1.22, and 0.56 ± 0.64, respectively). The patients with a lower severity score had slower disease progression.

CONCLUSION

This is the first cohort study of BCD in Taiwan, and we established a novel BCD severity index based on the molecular impact of different CYP4V2 variants. More severe impairment of CYP4V2 protein led to a more severe disease course with earlier progression. Our results could be helpful in identifying a therapeutic window for patients with BCD.