Bietti Crystalline Retinopathy Confirmed by Mutation of CYP4V2 Gene in a Korean Patient

Dear Editor, Bietti crystalline retinal dystrophy (BCD) is an autoso-mal recessive retinal dystrophy first described in 1937. It is characterized by numerous yellow-white crystals on the retina, associated with retinal pigment epithelium (RPE) atrophy and choroidal sclerosis [1]. Crystals and complex lipid inclusions are found in choroidal fibroblasts, cornea, conjunctiva, and circulating lymphocytes, implying that this condition results from a systemic abnormality. Although many cases with the CYP4V2 gene mutation have been reported worldwide, the first report of BCD in a Korean patient with a CYP4V2 gene mutation was recently published [2]. Herein, we present a Korean case of BCD confirmed to have a CYP4V2 gene mutation, review the previously reported BCD cases and their causative mutations, and present the key structural features of BCD with a novel hypothesis and the genetic disparity between Asians and non-Asians. A 45-year-old man was referred to Seoul National University Bundang Hospital with impaired vision in both eyes. He had monocular diplopia, nyctalopia, and photop-sia, persisting for the previous 2 months. His medical history was otherwise unremarkable. Blood analysis and tests for autoantibodies revealed no abnormalities. At the initial examination, his uncorrected visual acu-ities were 12 / 20 in the right eye and 14 / 20 in the left eye, with refractive errors of-2.625 Dsph in the right eye and-2.250 Dsph in the left eye. Slit lamp examination revealed a few crystal deposits in the cornea. Fundoscopic examination showed numerous yellowish-white crystals over the whole retina. RPE degeneration was observed with choroi-dal atrophy, which was more severe in the posterior pole than in the peripheral area (Fig. 1A). Fundus fluorescein angiography showed a well-demar-cated window defect due to RPE degeneration and choroi-dal atrophy and punctate fluorescein blockage caused by RPE hypertrophy (Fig. 1B). Spectral-domain optical coherence tomography (Spectralis; Heidelberg Engineering, Heidelberg, Germany) showed generalized photoreceptor layer disruption and multiple small hyper-reflective crystals in the retina, RPE-choriocapillary complex, and cho-roidal layers (Fig. 1C). Multiple circular structures with a hyper-reflective core were also observed. A standard 24-2 static visual field test (showed central scotoma (Fig. 1D). A standard electroretinogram showed slightly reduced amplitudes, while multifocal electroretinogram revealed a loss of peak response in the fovea (Fig. 1E and 1F). The patient was diagnosed with BCD based on these characteristic features. Genetic analysis of the CYP4V2 gene revealed a c.802-8_810delinsGC homozygote mutation. After 6 months, his visual acuity and the ophthalmo-logic findings remained unchanged. Although BCD cases …