Phenotypic differences in the PRPH2 mutation in members of the same family assessed with OCT and OCTA

Abstract

Purpose : Central choroidal dystrophies comprise degenerative diseases of the retina where choroid is also affected. The main cause of these dystrophies is related to mutations in the PRPH2 gene involved in the formation and maintenance of outer segments discs of photoreceptors. This study analyzes the structural changes of the retina and the vascular network in some members of a Spanish family with different choroidal dystrophies.

Methods : Cross-sectional and comparative study of 4 family members. OCT images in the macula were analyzed quantitative and qualitatively. Outer and inner retina measurements were done in the fovea and parafovea. Slabs of superficial vascular plexus, intermediate and deep capillary plexuses and choriocapillaris and choroid vessels were obtained to study their morphology and possible degeneration signs. Alterations in the foveal avascular zone (FAZ) were also described.

Results : Different clinical findings were present among family members with the same PRPH2 mutation: half were diagnosed with central areolar choroidal dystrophy (CACD) while the rest showed extensive chorioretinal atrophy (ECA). Retinal degeneration was mainly located at fovea and parafovea in CACD patients and the outer nuclear layer thickness in the FAZ was considerably reduced. ECA patients showed a more general degeneration that spread out through the central retina. The third outer hyperreflective band in OCT, considered as outer segments phagocytosed by the retinal pigment epithelium, was the first one disrupted of the four outer bands. Vascular degeneration was similar among them. Capillary drop out areas were larger in the deep capillary plexus. Microaneurysms were mainly detected in the superficial vascular plexus and were more easily found at early stages. Intraretinal microvascular abnormalities and vascular loops were observed in retinal plexuses. Extensive degeneration areas of choriocapillaris were seen in OCTA images which allowed to visualize the structure of choroid vessels.

Conclusions : Same PRPH2 mutation among different family members can cause phenotypic variations since youth. Clinical diagnosis and stage disease can be more easily defined in chorioretinal dystrophies using OCT and OCTA.
Support. FEDER-PID2019-106230RB-I00. FPU16/04114, FPU18/02964. RETICS-FEDER RD16/0008/0016. Retina Asturias/Cantabria. FARPE-FUNDALUCE. IDIFEDER/2017/064, ACIF/2020/203. RD16/0008/0001.

This is a 2021 ARVO Annual Meeting abstract.