The reportedly non-consanguineous RP family of this study included six individuals in a two-generation pedigree originating from the North-East of Italy (Fig. 1).
Figure 1.
All family members were clinically and genetically investigated, including the female proband who was referred for RP (I:2), three affected relatives (I:3 the proband’s brother, II:2 and II:3 the proband’s sons), and two unaffected individuals i.e., the proband’s husband (I:1) and the wife of the eldest proband’s son (II:1). The parents of the proband and of her husband were deceased. In particular, the familial anamnesis did not reveal any specific history of RP/IRD in earlier generations, even though complete information was not available, especially regarding the proband’s father who died when he was just 46 years old without ever undergoing any ophthalmologic visit. Starting from the second or third decade of life, all patients with RP in the family experienced night blindness, followed by the bilateral diagnosis of progressive visual field constriction using standard automated perimetry (SAP). The last ophthalmic examinations of each family member were accomplished in September 2023. The findings collected during these visits are detailed in Table 1, together with anamnestic and genotypic data.
Table 1. Summary of demographic, anamnestic, clinical and genotypic findings.
ID / Sex /Age
|
Initial Symptom / Age at Onset (yo)
|
Refraction (ESD) OD / OS
|
BCVA (SE) OD / OS
|
SAP Visual Field MD (dB) OD / OS
|
IOP (mmHg) OD / OS
|
LOCS III (NO-NC-C-P) OD / OS
|
CRT (SD-OCT) OD / OS
|
ff-ERG Amplitude (mVolts) OD / OS
|
EYS Genotype-Phenotype Correlation
|
First Report of EYS Variants
|
I:2 / F / 60 yo *
|
NB / 26
|
-1.25 / -2.00
|
20/80 / 20/63
|
-32.16 / -31.93
|
14 / 16
|
1-1-0-2 / 1-1-0-2
|
143 / 155
|
0.0 / 0.0
|
Het-Ex29/Het-Ex33 / RP
|
Ref: 20, 25
|
I:3 / M / 54 yo
|
NB / 20
|
-6.00 / -5.25
|
20/125 / HM
|
-31.88 / NF
|
16 / 10
|
1-1-0-2 / NF
|
135 / NF
|
0.0 / NF
|
Het-Ex29/Het-Ex33 / RP
|
Ref: 20, 25
|
I:1 / M / 62 yo
|
None / NA
|
+1.50 / +2.00
|
20/20 / 20/20
|
-0.71 / -0.85
|
18 / 18
|
1-1-0-0 / 1-1-0-0
|
251 / 254
|
244.6 / 245.8
|
Het-Ex33 / NR
|
Ref: 20
|
II:2 / M / 38 yo
|
NB / 30
|
-5.50 / -6.00
|
20/25 / 20/20
|
-22.76 / -20.37
|
16 / 14
|
0-0-0-1 / 0-0-0-1
|
304 / 298
|
112.3 / 106.8
|
Het-Ex29/Het-Ex33 / RP
|
Ref: 20, 25
|
II:3 / M / 35 yo
|
NB / 28
|
-2.75 / -3.25
|
20/20 / 20/25
|
-30.19 / -31.16
|
16 / 16
|
0-0-0-1 / 0-0-0-1
|
315 / 293
|
78.9 / 72.6
|
Hom-Ex33 / RP
|
Ref: 20
|
II:1 / F / 37 yo
|
None / NA
|
+0.50 / +0.25
|
20/20 / 20/20
|
-0.34 / -0.27
|
16 / 16
|
0-0-0-0 / 0-0-0-0
|
259 / 256
|
268.9 / 267.5
|
Normal / NR
|
NA
|
Abbreviations: ID, Identification code of patients; yo, year-old; F, Female; *, Proband; M, Male; NB, Night Blindness; NA, Not Applicable; ESD, Equivalent Spherical Diopters; OD, Oculus Dexter; OS, Oculus Sinister; BCVA, Best Corrected Visual Acuity; SE, Snellen Equivalent; HM, hand movements; SAP, Standard Automated Perimetry (Humphrey 30-2 visual field, SITA standard strategy, and III-white stimulus); MD, Mean Deviation; dB, Decibel; NF, Not Feasible; IOP, Intraocular Pressure; LOCS III, Lens Opacities Classification System III; NO, Nuclear Opalescence; NC, Nuclear Color; C, Cortical cataract; P, Posterior subcapsular cataract; CRT, Central Retinal Thickness; SD-OCT, Spectral-Domain Optical Coherence Tomography; ff-ERG, full-field Electroretinography; EYS, Eyes Shut Homolog gene; Het-Ex29/Het-Ex33, compound heterozygosity in EYS exon 29 [c.(5927þ1_5928-1)_(6078þ1_6079-1)del] and EYS exon 33 [c.6714delT]; RP, Retinitis Pigmentosa; Het-Ex33, single heterozygosity in EYS exon 33 [c.6714delT]; NR, Normal Retina; Hom-Ex33, homozygosity in EYS exon 33 [c.6714delT]; Ref, reference’s number in this article.
Both eyes of all individuals were fully assessed, with the exception of the left eye of the proband’s brother (I:3) which was not explorable because of a total corneal leukoma with dense white scar due to perforating ocular trauma occurred when he was 41 years old. After the most appropriate correction of the refractive errors, a marked reduction of best-corrected visual acuity (BCVA) was present only in the eyes of RP patients over 50 years of age (I:2 and I:3; Table 1). These BCVA losses appeared to be independent from the extents of the posterior subcapsular cataract, whereas their magnitudes were proportional to the severity of the central retinal atrophy diagnosed by the autofluorescence (AF) imaging of the macular area (I:2 and I:3; Fig. 2A). In both eyes of patients in the fourth decade of life, AF imaging revealed the typical, RP-related, hyper-autofluorescent perifoveal rings (II:2 and II:3; Fig. 2A), whose larger diameters were consistent with the unexpected findings of less aggressive retinopathy in the oldest brother, characterized by more preserved visual fields in comparison with the youngest one (II:2 vs. II:3; Fig.3).
Figure 2.
Figure 3.
Ophthalmoscopic fundus examination of all RP patients showed variable amounts of vitreous degeneration, optic disc pallor, attenuated retinal vessels, and degenerative changes of the retinal pigment epithelium with mid-peripheral bone spicule-shaped pigment deposits. As well, the tracings of full-field electroretinography (ff-ERG) were extinguished or significantly reduced (Table 1). Spectral-domain optical coherence tomography (SD-OCT) detailed moderate-to-severe macular degenerative changes, variably involving the vitreomacular interface, inner and outer retinal layers, and RPE (Fig. 2B). None of the RP patients showed additional disorders suggestive of either Usher’s syndrome or other syndromic RPs. Finally, complete ophthalmologic examination, SAP, SD-OCT, and ff-ERG were also conducted on asymptomatic family members (I:1 and II:1), without showing any significant ocular disorder (Table 1). Phenotypically, the family pedigree was therefore characterized by an apparent autosomal dominant RP inheritance, with affected male and female individuals belonging to two contiguous generations - see the blue elements inserted in Fig. 1. However, genotypic assessment by means of NGS enhanced by bioinformatic analysis for the detection of copy-number variations (CNVs), followed by validation with Multiplex Dependent Probe Amplification (MLPA) assay, allowed the unexpected identification of two known pathogenic RP variants in different exons of the EYS gene (RefSeq NM_001142800.2): i. the frameshift variant c.6714delT p.(Ile2239Serfs*17) in exon 33; [11,15,20] ii. the recurrent deletion c.(5927þ1_5928-1)_(6078þ1_6079-1) of exon 29. [25,26] (Fig. 4)
Figure 4.
Particularly, in patients I:2, I:3, and II:3, both pathogenic variants were identified in compound heterozygosity, whereas patient II:2 was homozygous for c.6714delT. In this pseudodominant pedigree, the molecular characterization of both EYS alleles in the proband’s husband (I:1) revealed the condition of heterozygous healthy carrier for the frameshift mutation c.6714delT in exon 33, whereas no significant EYS variants were observed in the wife of the eldest proband’s son (II:1) (Table 1).