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

ABSTRACT Objective To investigate the genotype and long-term clinical phenotype of patients with Bietti crystalline dystrophy (BCD) in Korea and Japan. Design Retrospective case series. Subjects We analyzed the cases of 62 patients with clinical features of BCD who harbor pathogenic biallelic CYP4V2 variants in their homozygote or compound heterozygote. Methods Data were collected from patient charts including, age, best-corrected visual acuity (BCVA), Goldmann perimetry, fundus photography, optical coherence tomography, fundus autofluorescence, and electroretinogram. We compared the clinical course of the patients with homozygous c.802-8_810del17insGC [Exon7del], the most common mutation in the East Asian population, with those of the patients with other genotypes. Main Outcome Measures BCVA, visual field (VF), and their changes during follow-up. Results The mean age at the first visit was 55.2 years, with the mean follow-up of 7.1 years. The mean BCVAs at the first and last visits were 0.28 logarithm of the minimum angle of resolution (logMAR) and 0.89 logMAR, respectively. In genetic testing, c.802-8_810del17insGC was detected in 86 of 124 alleles of the subjects, and 36 patients were homozygous for this mutation. The age, BCVA, VF area, central foveal thickness, and abnormal hypoautofluorescent area at either the first visit or the last visit were not different between the Exon7del homozygotes and the others. The mean BCVA changes per year were 0.089 logMAR in the Exon7del homozygotes and 0.089 logMAR in the others. An age- and sex-adjusted linear regression analysis showed no association between the Exon7del homozygote status and the rate of vision loss. Characteristic crystalline deposits in the posterior pole were generally observed in younger patients and disappeared over time along with progressive retinochoroidal atrophy. Conclusions BCD patients with a homozygote for c.802-8_810del17insGC accounted for >50% of this cohort of Korean and Japanese patients, and the clinical effect of this deleterious variant was not severe in the spectrum of CYP4V2 retinopathy.