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R. Sui, H. Zhang, F. Xu, Q. Zhou; Clinical and Molecular Analysis of Chinese Patients With Bietti Crystalline Retinopathy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2600.
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Bietti crystalline retinopathy (BCR) is an autosomal recessive inherited disorder characterized by multiple glistening crystals scattered over the fundus. Retinal pigment epithelium (RPE) and choroidal atrophy are associated clinical findings. CYP4V2, encoding a member of cytochrome p450 (CYP450) protein family, was identified as the causative gene. A cohort of Chinese patients were studies clinically and CYP4V2 gene was screened.
Sixteen patients from 9 unrelated Chinese families were recruited for this study. The diagnosis of BCR was made on the base of clinical evaluation and family history. Detailed ocular examinations including visual acuity, slit lamp, fundus fluorescein angiography, electroretinography (ERG), optical coherent topography (OCT) and visual field were performed for affected subjects. Peripheral blood was obtained from all patients and their family members for genomic DNA extraction. The coding region of CYP4V2 were amplified by PCR and screened for mutation by direct DNA sequencing.
Clinical examination revealed typical features of BCR with many small yellowish-sparkling crystals at the posterior pole and mid-periphery retina. Visual acuity varied from 20/200 to 20/20. ERG demonstrated changes from mild decreased a and b waves to nonrecordable waveform. OCT revealed thinning of IS/OS complex and intraretinal crystals in all patients. Sequencing of CYP4V2 identified six disease-causing mutations including three novel mutations (Q259K, V397I and IVS6-7C→T) and three reported (IVS6-8del17bp insGC, H331P and IVS8-2A→G). None of the novel mutations was detected in fifty Chinese normal controls. IVS6-8del17bp insGC (exon 7 del) change was the most mutation. It was detected as homozygous in eight patients and as heterozygous in five patients.
IVS6-8del17bp insGC Allele may be especially prevalent among patients with BCR in China. Phenotypic variability was found and no obvious genotype-phenotype relationship was observed.
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