Deep phenotyping of PROM1-associated retinal degeneration

Phenotyping and genotyping inherited retinal diseases: Molecular genetics, clinical and imaging features, and therapeutics of macular dystrophies, cone and cone-rod dystrophies, rod-cone dystrophies, Leber congenital amaurosis, and cone dysfunction syndromes

Inherited retinal diseases (IRD) are a leading cause of blindness in the working age population and in children. The scope of this review is to familiarise clinicians and scientists with the current landscape of molecular genetics, clinical phenotype, retinal imaging and therapeutic prospects/completed trials in IRD. Herein we present in a comprehensive and concise manner: (i) macular dystrophies (Stargardt disease (ABCA4), X-linked retinoschisis (RS1), Best disease (BEST1), PRPH2-associated pattern dystrophy, Sorsby fundus dystrophy (TIMP3), and autosomal dominant drusen (EFEMP1)), (ii) cone and cone-rod dystrophies (GUCA1A, PRPH2, ABCA4, KCNV2 and RPGR), (iii) predominant rod or rod-cone dystrophies (retinitis pigmentosa, enhanced S-Cone syndrome (NR2E3), Bietti crystalline corneoretinal dystrophy (CYP4V2)), (iv) Leber congenital amaurosis/early-onset severe retinal dystrophy (GUCY2D, CEP290, CRB1, RDH12, RPE65, TULP1, AIPL1 and NMNAT1), (v) cone dysfunction syndromes (achromatopsia (CNGA3, CNGB3, PDE6C, PDE6H, GNAT2, ATF6), X-linked cone dysfunction with myopia and dichromacy (Bornholm Eye disease; OPN1LW/OPN1MW array), oligocone trichromacy, and blue-cone monochromatism (OPN1LW/OPN1MW array)). Whilst we use the aforementioned classical phenotypic groupings, a key feature of IRD is that it is characterised by tremendous heterogeneity and variable expressivity, with several of the above genes associated with a range of phenotypes.

Progression of PROM1-Associated Retinal Degeneration as Determined by Spectral-Domain Optical Coherence Tomography Over a 24-Month Period

PURPOSE

To evaluate the progression of atrophy as determined by spectral-domain optical coherence tomography (SD-OCT) in patients with molecularly confirmed PROM1-associated retinal degeneration (RD) over a 24-month period.

DESIGN

International, multicenter, prospective case series.

METHODS

A total of 13 eyes (13 patients) affected with PROM1-associated RD were enrolled at 5 sites and SD-OCT images were obtained at baseline and after 24 months. Loss of mean thickness (MT) and intact area were estimated after semi-automated segmentation for the following individual retinal layers in the central subfield (CS), inner ring, and outer ring of the ETDRS grid: retinal pigment epithelium (RPE), outer segments (OS), inner segments (IS), outer nuclear layer (ONL), inner retina (IR), and total retina (TR).

RESULTS

Statistically significant losses of thickness of RPE and TR were detected in the CS and inner ring and of ONL and IS in the outer ring (all P < .05); a statistically significant decrease in the intact area of RPE and IS was observed in the inner ring, and of ONL in the outer ring (all P < .05); the change in MT and the intact area of the other layers showed a trend of decline over an observational period of 24 months.

CONCLUSIONS

Significant thickness losses could be detected in outer retinal layers by SD-OCT over a 24-month period in patients with PROM1-associated retinal degeneration. Loss of thickness and/or intact area of such layers may serve as potential endpoints for clinical trials that aim to slow down the disease progression of PROM1-associated retinal degeneration.

Genetic and clinical characteristics of PROM1-related retinal degeneration in Korean

This scientific report aims to comprehensively describe the genetic and clinical characteristics of PROM1-related retinal degeneration in Korean patients. Medical records of patients diagnosed with retinal dystrophy who underwent comprehensive ophthalmologic examination and genetic testing at Samsung Medical Center between January 2016 and April 2023 were retrospectively reviewed. Genetic testing included targeted gene panel sequencing and Sanger sequencing, with diagnosis based on the presence of a "Likely Pathogenic" or "Pathogenic Variant" in the PROM1 gene, as determined by the ACMG criteria. The study identified seven patients from five unrelated families with PROM1-related retinal degeneration, all carrying the autosomal dominant variant PROM1 p.R373C; no other PROM1 gene variants were detected. All patients exhibited degenerative retinal area within the macula, with peripheral retinal degeneration observed in five patients. Substantial interfamilial and intrafamilial variability was observed in the extent of macular and peripheral degeneration. Ultra-widefield autofluorescence imaging and fluorescein angiography aided in the detection of mild peripheral degeneration in one case. In conclusion, the autosomal dominant variant PROM1 p.R373C constitutes a significant proportion of PROM1-related retinal degeneration cases in the Korean population. The observed clinical heterogeneity may suggests the potential influence of additional genetic, epigenetic, and environmental factors on disease phenotypes.