Table 1.

Molecular Genetic Testing Used in Bietti Crystalline Dystrophy

Gene 1MethodProportion of Pathogenic Variants 2 Detectable by Method
CYP4V2 Sequence analysis 3>93% - 97.7% 4, 5, 6
Gene-targeted deletion/duplication analysis 72 individuals 8, 9
1.
2.

See Molecular Genetics for information on allelic variants detected in this gene.

3.

Sequence analysis detects variants that are benign, likely benign, of uncertain significance, likely pathogenic, or pathogenic. Variants may include small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

4.

Pathogenic variants were identified in 95.4% (N=109) families or 93.6% of alleles [Xiao et al 2011].

5.

In a study from Japan, eight probands were found to have mutation of CYP4V2, including seven with the c.802-8_810delinsGC (reported as IVS6-8_c.810del/insGC) variant, suggesting a founder effect.

6.

CP4V2 pathogenic variants have been detected in 97.7% of individuals of Chinese descent [Zhang et al 2018].

7.

Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include: quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications.

8.

A large deletion encompassing exon 8 was reported by Zhang et al [2018].

9.

A ~4-Mb deletion encompassing CYP4V2 and several adjacent genes was identified in an individual with BCD from Germany [Astuti et al 2015].

From: Bietti Crystalline Dystrophy

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