A Novel Compound Heterozygous Mutation in the CYP4V2 Gene in a Japanese Patient with Bietti's Crystalline Corneoretinal Dystrophy

Abstract

Purpose: To describe the clinical and genetic characteristics of a Japanese family in which one member exhibited Bietti's crystalline corneoretinal dystrophy (BCD).

Methods: Using direct sequencing, mutation screening was performed in the CYP4V2 gene of both the patient with BCD and her daughter. Ophthalmic examinations were performed to determine the clinical features of both subjects.

Results: The 64-year-old female patient had a bilateral visual acuity of 0.4. Slit lamp examination revealed bilateral crystalline-like deposits at the superior limbus of the cornea. Fundus examination revealed there was chorioretinal atrophy along with numerous glistening yellowish-white crystalline deposits that were scattered throughout the posterior pole and the mid-peripheral retina. Standard flash electroretinography showed an extinguished electroretinogram and Goldmann kinetic perimetry detected a relative scotoma. Genetic analysis revealed that the patient had a heterozygous mutation in the CYP4V2 gene (IVS6-8delTCATACAGGTCATCGCG/GC), which is the most commonly found mutation in Japanese patients with BCD. Furthermore, the patient was also shown to have a novel heterozygous point mutation in exon 9 of the CYP4V2 gene (c.1168C>T). In contrast, her daughter exhibited no clinical findings for BCD even though she carried the same heterozygous mutation in the CYP4V2 gene (c.1168C>T).

Conclusion: A novel compound heterozygous mutation was found in the CYP4V2 gene of a patient with BCD. This previously unreported c.1168C>T mutation causes a missense mutation (p.R390C) in the CYP4V2 protein.

Keywords: Bietti's crystalline corneoretinal dystrophy; CYP4V2 gene; Retinal dystrophy; Retinitis pigmentosa.

Fig. 1

Slit lamp biomicroscopic findings showing crystalline-like corneal deposits in the superior limbal area.

Fig. 2

Fundus photograph of the left eye showing numerous crystalline-like deposits and chorioretinal degeneration in the posterior pole.

Fig. 3

Nucleotide sequence of the CYP4V2 gene at the exon-intron boundary area of the exon 7, showing a heterozygous IVS6-8delTCATACAGGTCATCGCG/GC mutation in the patient with BCD. Her daughter exhibited a normal sequence similar to the wild-type control. Arrows show positions of silent mutations at IVS6-7(C>T) in a control subject and c.810G>T (p.A270A) in the phenotypically normal daughter.

Fig. 4

Nucleotide sequence of the CYP4V2 gene around nucleotide 1168 in the exon 9, showing the heterozygous missense mutations (c.1168C>T) that were found in both the patient and her daughter. These mutations resulted in p.R390C.