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.
Keywords: Bietti's dystrophy; CYP4V2 gene; corneoretinal dystrophy; mutation.