A Novel Pathogenic Variant in NDP Gene With Incomplete Penetrance Manifests as X-Linked Familial Exudative Vitreoretinopathy

Identification of Two Novel Variants in the LRP5 Gene that Cause Familial Exudative Vitreoretinopathy

Background: Familial exudative vitreoretinopathy (FEVR, OMIM 133780) is a severe inherited eye disease characterized by abnormal development of the retinal vasculature. Variants in the reported genes account for ∼50% of total FEVR cases. However, the pathogenesis of other 50% of FEVR cases remains unclear. Therefore, it is crucial to identify novel variants responsible for the pathogenesis of FEVR. Aims: To find causative variants responsible for FEVR in two Han Chinses families. Materials and Methods: We recruited two families with two FEVR patients and applied exome sequencing on the genomic DNA samples from the probands. Sanger sequencing was performed for variant validation. Western blot analysis and luciferase assays were performed to test the expression levels and activity of mutant proteins. Results: We identified two novel missense variants in the LRP5 gene (NM_002335), namely c.1176 C > A (p.Asp392Glu) and c.2435 A>C (p.Asp812Ala), inherited in an autosomal dominant manner. Both variants significantly reduced Norrin/β-catenin signaling activity without affecting the expression of the LRP5 protein. Conclusion: This study expands the variant spectrum of the LRP5 gene for FEVR, providing valuable information for prenatal counseling and molecular diagnosis of FEVR.

INTRAVITREAL RANIBIZUMAB TREATMENT FOR ADVANCED FAMILIAL EXUDATIVE VITREORETINOPATHY WITH HIGH VASCULAR ACTIVITY

PURPOSE

To determine the efficacy of intravitreal ranibizumab (IVR) treatment for advanced familial exudative vitreoretinopathy with high vascular activity.

METHODS

The retrospective interventional case series included 28 eyes (20 patients) that had IVR in combination or not with other treatment, for Stage 3 to 5 familial exudative vitreoretinopathy with active fibrovascular proliferation and prominent subretinal exudation. Outcome measures were fundus features after treatment, associated clinical variables, and genetic mutations.

RESULTS

The age of patients at the first IVR ranged from 0.2 to 36 months. An average of 1.3 IVR injections per eye were given. Familial exudative vitreoretinopathy regressed in 16 (57%) eyes and progressed in 12 eyes (43%) after IVR. Laser and/or vitrectomy was performed on 13 eyes. The retina was reattached in 22 eyes (78%) after 24 to 58 months follow-up. Clinical variables associated with progression after IVR were preexisting fibrovascular proliferation over one quadrant and persistent vascular activity after the initial injection (P < 0.05). Familial exudative vitreoretinopathy-causative genetic mutations in 11 patients were related to variable response to IVR treatment.

CONCLUSION

Intravitreal ranibizumab treatment may effectively regress advanced familial exudative vitreoretinopathy with high vascular activity in selected cases. Different treatment outcomes may be relevant to variable presentation and genetic heterogeneity of familial exudative vitreoretinopathy.