A founder variant expands the phenotype of WNT7B-related PDAC syndrome.

Pulmonary hypoplasia, Diaphragmatic anomalies, Anophthalmia/microphthalmia, and Cardiac defects (PDAC) syndrome is a genetically heterogeneous multiple congenital malformation syndrome. Although pathogenic variants in RARB and STRA6 are established causes of PDAC, many PDAC cases remain unsolved at the molecular level. Recently, we proposed biallelic WNT7B variants as a novel etiology based on several families with typical features of PDAC syndrome albeit with variable expressivity. Here, we report three patients from two families that share a novel founder variant in WNT7B (c.739C > T; Arg247Trp). The phenotypic expression of this variant ranges from typical PDAC features to isolated genitourinary anomalies. Similar to previously reported PDAC-associated WNT7B variants, this variant was found to significantly impair WNT7B signaling activity further corroborating its proposed pathogenicity. This report adds further evidence to WNT7B-related PDAC and expands its variable expressivity.

Beyond the exome: utility of long-read whole genome sequencing in exome-negative autosomal recessive diseases.

BACKGROUND: Long-read whole genome sequencing (lrWGS) has the potential to address the technical limitations of exome sequencing in ways not possible by short-read WGS. However, its utility in autosomal recessive Mendelian diseases is largely unknown. METHODS: In a cohort of 34 families in which the suspected autosomal recessive diseases remained undiagnosed by exome sequencing, lrWGS was performed on the Pacific Bioscience Sequel IIe platform. RESULTS: Likely causal variants were identified in 13 (38%) of the cohort. These include (1) a homozygous splicing SV in TYMS as a novel candidate gene for lethal neonatal lactic acidosis, (2) a homozygous non-coding SV that we propose impacts STK25 expression and causes a novel neurodevelopmental disorder, (3) a compound heterozygous SV in RP1L1 with complex inheritance pattern in a family with inherited retinal disease, (4) homozygous deep intronic variants in LEMD2 and SNAP91 as novel candidate genes for neurodevelopmental disorders in two families, and (5) a promoter SNV in SLC4A4 causing non-syndromic band keratopathy. Surprisingly, we also encountered causal variants that could have been identified by short-read exome sequencing in 7 families. The latter highlight scenarios that are especially challenging at the interpretation level. CONCLUSIONS: Our data highlight the continued need to address the interpretation challenges in parallel with efforts to improve the sequencing technology itself. We propose a path forward for the implementation of lrWGS sequencing in the setting of autosomal recessive diseases in a way that maximizes its utility.

Presumed uremic optic neuropathy in a patient with Senior-Loken syndrome.

A patient who had been diagnosed with infantile retinal dystrophy developed renal failure in his twenties, at which time the diagnosis was revised to Senior-Loken syndrome. He was poorly compliant. At 36 years old, he experienced a sudden drop in visual acuity in the setting of cramping and fatigue and was found to be in uremic crisis. Six months after the event and its treatment, his vision failed to improved. Optic nerve pallor was out of proportion to the retinal dystrophy, and the presumed reason for his new visual loss was uremic optic neuropathy. The patient's younger sister also had been diagnosed with infantile retinal dystrophy, and metabolic screening confirmed subclinical renal dysfunction that was to be carefully followed going forward. Infantile retinal dystrophy can be associated with later systemic disease. Early detection of such disease can potentially decrease morbidity. Patients with retinal dystrophy can develop new visual loss from causes other than the retinopathy itself.

Full-field electroretinography - when do we need it?

Multimodal imaging and genetic testing allow sophisticated assessment of suspected inherited retinal disease. Given the availability of such technology, some question whether the full-field electrogram (ffERG) is needed anymore. In fact, a ffERG remains essential for certain clinical scenarios. The goal of this case-based review is to provide a clear understanding of what clinical situations warrant a ffERG. All practicing ophthalmologists should be familiar with this information.

KCNV2-associated retinopathy: genotype-phenotype correlations - KCNV2 study group report 3.

BACKGROUND/AIMS: To investigate genotype-phenotype associations in patients with KCNV2 retinopathy. METHODS: Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants, electroretinography (ERG) and retinal imaging. Subjects were grouped according to the combination of KCNV2 variants-two loss-of-function (TLOF), two missense (TM) or one of each (MLOF)-and parameters were compared. RESULTS: Ninety-two patients were included. The mean age of onset (mean±SD) in TLOF (n=55), TM (n=23) and MLOF (n=14) groups was 3.51±0.58, 4.07±2.76 and 5.54±3.38 years, respectively. The mean LogMAR BCVA (±SD) at baseline in TLOF, TM and MLOF groups was 0.89±0.25, 0.67±0.38 and 0.81±0.35 for right, and 0.88±0.26, 0.69±0.33 and 0.78±0.33 for left eyes, respectively. The difference in BCVA between groups at baseline was significant in right (p=0.03) and left eyes (p=0.035). Mean outer nuclear layer thickness (±SD) at baseline in TLOF, MLOF and TM groups was 37.07±15.20 µm, 40.67±12.53 and 40.38±18.67, respectively, which was not significantly different (p=0.85). The mean ellipsoid zone width (EZW) loss (±SD) was 2051 µm (±1318) for patients in the TLOF, and 1314 µm (±965) for MLOF. Only one patient in the TM group had EZW loss at presentation. There was considerable overlap in ERG findings, although the largest DA 10 ERG b-waves were associated with TLOF and the smallest with TM variants. CONCLUSIONS: Patients with missense alterations had better BCVA and greater structural integrity. This is important for patient prognostication and counselling, as well as stratification for future gene therapy trials.

LEPREL1 -RELATED GIANT RETINAL TEAR DETACHMENTS MIMIC THE PHENOTYPE OF OCULAR STICKLER SYNDROME.

PURPOSE: To describe the features of retinal detachments and high myopia in patients with novel pathogenic variants in LEPREL1 and report a possible association with nephropathy. METHODS: Retrospective study of 10 children with biallelic LEPREL1 pathogenic variants. Data included ophthalmic features, surgical interventions, and genetic and laboratory findings. RESULTS: 10 patients (8 females) from three families with homozygous (2) or compound heterozygous (1) variants in LEPREL1 were included. At presentation, mean age was 9.9 ± 2.6 years. Mean axial length was 28.9 ± 1.9 mm and mean refraction was -13.9 ± 2.8 diopters. Bilateral posterior subcapsular cataracts were present in eight patients (80%), with lens subluxation in five eyes of three patients (30%). Rhegmatogenous retinal detachments (RRD), associated with giant retinal tears (GRT), developed in seven eyes of five patients (50%) at a mean age of 14.14 ± 5.9 years. Six were successfully reattached with mean Snellen best-corrected visual acuity improving from 20/120 preoperatively to 20/60 at last follow-up. Urinalysis in nine patients revealed microhematuria and/or mild proteinuria in six patients (67%). CONCLUSION: LEPREL1 -related high myopia confers a high risk of early-onset GRT-related RRD. The ocular phenotype may be confused with that of ocular Stickler syndrome if genetic testing is not performed. Further investigations into a potential association with renal dysfunction are warranted.

RPGRIP1-related retinal disease presenting as isolated cone dysfunction.

PURPOSE: Bialleic RPGRIP1 pathogenic variants are typically associated with severe Leber congenital amaurosis (non-recordable electroretinography [ERG]) and less commonly with cone-rod dystrophy. This report highlights isolated cone dysfunction as an alternative RPGRIP1-related presenting phenotype. METHODS: Retrospective case series. RESULTS: Four individuals (two sibships from two unrelated families) had low vision, nystagmus, photophobia, and a grossly normal retinal appearance since soon after birth. ERG confirmed non-recordable photopic function with normal scotopic function. Genetic testing revealed affected members from the two families to harbor two different homozygous RPGRIP1 variants (Family 1: c.3565C>T; p.Arg1189*; Family 2: c.2711_2741delinsATATTAG; p.Gly904_Lys914delinsAspIIeArg). Follow-up for Family 1 revealed deterioration of pan-retinal function (non-recordable ERGs by 11 and 7 years old) and thus a final diagnosis of cone-rod dystrophy. Follow-up for Family 2 showed stable retinal function (normal ERG scotopic tracings maintained at 12 and 21 years old) and thus a diagnosis of isolated cone dysfunction. CONCLUSIONS: Isolated cone dysfunction that progresses to pan-retinal dysfunction or remains relatively stationary is an alternative phenotype related to biallelic RPGRIP1 pathogenic variants.

The genomic landscape of rare disorders in the Middle East.

BACKGROUND: Rare diseases collectively impose a significant burden on healthcare systems, especially in underserved regions, like the Middle East, which lack access to genomic diagnostic services and the associated personalized management plans. METHODS: We established a clinical genomics and genetic counseling facility, within a multidisciplinary tertiary pediatric center, in the United Arab Emirates to locally diagnose and manage patients with rare diseases. Clinical genomic investigations included exome-based sequencing, chromosomal microarrays, and/or targeted testing. We assessed the diagnostic yield and implications for clinical management among this population. Variables were compared using the Fisher exact test. Tests were 2-tailed, and P < .05 was considered statistically significant. RESULTS: We present data on 1000 patients with rare diseases (46.2% females; average age, 4.6 years) representing 47 countries primarily from the Arabian Peninsula, the Levant, Africa, and Asia. The cumulative diagnostic yield was 32.5% (95% CI, 29.7-35.5%) and was higher for genomic sequencing-based testing than chromosomal microarrays (37.9% versus 17.2%, P = 0.0001) across all indications, consistent with the higher burden of single gene disorders. Of the 221 Mendelian disorders identified in this cohort, the majority (N = 184) were encountered only once, and those with recessive inheritance accounted for ~ 62% of sequencing diagnoses. Of patients with positive genetic findings (N = 325), 67.7% were less than 5 years of age, and 60% were offered modified management and/or intervention plans. Interestingly, 24% of patients with positive genetic findings received delayed diagnoses (average age, 12.4 years; range 7-37 years), most likely due to a lack of access to genomic investigations in this region. One such genetic finding ended a 15-year-long diagnostic odyssey, leading to a life-threatening diagnosis in one patient, who was then successfully treated using an experimental allogenic bone marrow transplant. Finally, we present cases with candidate genes within regions of homozygosity, likely underlying novel recessive disorders. CONCLUSIONS: Early access to genomic diagnostics for patients with suspected rare disorders in the Middle East is likely to improve clinical outcomes while driving gene discovery in this genetically underrepresented population.

Bi-allelic variants in WNT7B disrupt the development of multiple organs in humans.

BACKGROUND: Pulmonary hypoplasia, Diaphragmatic anomalies, Anophthalmia/microphthalmia and Cardiac defects delineate the PDAC syndrome. We aim to identify the cause of PDAC syndrome in patients who do not carry pathogenic variants in RARB and STRA6, which have been previously associated with this disorder. METHODS: We sequenced the exome of patients with unexplained PDAC syndrome and performed functional validation of candidate variants. RESULTS: We identified bi-allelic variants in WNT7B in fetuses with PDAC syndrome from two unrelated families. In one family, the fetus was homozygous for the c.292C>T (p.(Arg98*)) variant whereas the fetuses from the other family were compound heterozygous for the variants c.225C>G (p.(Tyr75*)) and c.562G>A (p.(Gly188Ser)). Finally, a molecular autopsy by proxy in a consanguineous couple that lost two babies due to lung hypoplasia revealed that both parents carry the p.(Arg98*) variant. Using a WNT signalling canonical luciferase assay, we demonstrated that the identified variants are deleterious. In addition, we found that wnt7bb mutant zebrafish display a defect of the swimbladder, an air-filled organ that is a structural homolog of the mammalian lung, suggesting that the function of WNT7B has been conserved during evolution for the development of these structures. CONCLUSION: Our findings indicate that defective WNT7B function underlies a form of lung hypoplasia that is associated with the PDAC syndrome, and provide evidence for involvement of the WNT-ß-catenin pathway in human lung, tracheal, ocular, cardiac, and renal development.

PMEL is mutated in oculocutaneous albinism.

Oculocutaneous albinism (OCA) is a group of Mendelian disorders characterized by hypopigmentation of skin, hair and pigmented ocular structures. While much of the genetic heterogeneity of OCA has been resolved, many patients still lack a molecular diagnosis following exome sequencing. Here, we report a consanguineous family in which the index patient presented with OCA and Hirschsprung disease but tested negative for known genetic causes of OCA. Instead, he was found to have a homozygous presumptive loss of function variant in PMEL. PMEL encodes a scaffolding protein that is essential for the normal maturation of melanosomes and normal deposition of the melanin pigment therein. Numerous PMEL vertebrate ortholog mutants have been reported and all were characterized by conspicuous pigmentary abnormalities. We suggest that the patient we report is the first human equivalent of PMEL loss of function.

ADAMTS18-related anterior segment dysgenesis mistaken as Axenfeld-Rieger syndrome.

Axenfeld-Rieger spectrum is a range of anterior segment dysgenesis (ASD) phenotypes often related to heterozygous pathogenic variants in the ocular transcription factor genes FOXC1 or PITX2. Microcornea with myopic chorioretinal atrophy, a less common ASD, is distinct, recognizable, and secondary to biallelic pathogenic variants in the metalloproteinase gene ADAMTS18. This report describes the case of a boy with ADAMTS18-related ASD that was mistaken for Axenfeld-Rieger syndrome and highlights distinguishing features.

Congenital Cranial Dysinnervation Disorder Complicated by Ipsilateral Orbital Choriostoma.

A 20-year-old woman with right-sided congenital cranial dysinnervation disorder (exotropia, ophthalmoplegia, and ptosis) presented for strabismus surgery. Exploration of the right eye confirmed abnormal extraocular muscles. Lateral rectus recession with medial rectus plication and inferior oblique recession improved primary position ocular alignment. However, an unusual pattern of inferior chemosis developed postoperatively and persisted during the next month. Excision and histologic examination of this tissue revealed areas of lacrimal gland and cartilage with surrounding inflammation, suggestive of a disrupted orbital choriostoma. [J Pediatr Ophthalmol Strabismus. 2022;59(6):e66-e68.].

Anterior segment dysgenesis: Insights into the genetics and pathogenesis.

Childhood glaucoma is a treatable cause of blindness, provided it is recognized, diagnosed, and treated in time. WHO has estimated that it is responsible for Blind Years second only to cataracts. The fundamental pathophysiology of all childhood glaucoma is impaired outflow through the trabecular meshwork. Anterior segment Dysgeneses (ASD) are a group of non-acquired ocular anomalies associated with glaucoma, characterized by developmental abnormalities of the tissues of the anterior segment. The cause is multifactorial, and many genes are involved in the development of the anterior segment. Over the last decade, molecular and developmental genetic research has transformed our understanding of the molecular basis of ASD and the developmental mechanisms underlying these conditions. Identifying the genetic changes underlying ASD has gradually led to the recognition that some of these conditions may be parts of a disease spectrum. The characterization of genes responsible for glaucoma is the critical first step toward developing diagnostic and screening tests, which could identify individuals at risk for disease before irreversible optic nerve damage occurs. It is also crucial for genetic counseling and risk stratification of later pregnancies. It also aids pre-natal testing by various methods allowing for effective genetic counseling. This review will summarize the known genetic variants associated with phenotypes of ASD and the possible significance and utility of genetic testing in the clinic.

A Stargardt disease-like phenotype in GAS8-related primary ciliary dyskinesia.

PURPOSE: Ciliopathies are broadly classified as non-motile or motile (primary ciliary dyskinesia). Early-onset retinal dystrophy is common in non-motile ciliopathy, but retinal dystrophy is not considered a feature of primary ciliary dyskinesia. The subject of this report is woman referred as a case of Stargardt disease who in fact had retinal dystrophy apparently related to GAS8-related primary ciliary dyskinesia. METHODS: Retrospective case report. RESULTS: A 43-year-old Emirati woman was referred for further evaluation of Stargardt disease. Her only ophthalmic complaints were related to dry eye disease. Past ocular history was significant for refractive surgery in her early 30's. Past medical history was significant for primary ciliary dyskinesia, which included recurrent bronchiectasis and sino-pulmonary infections since childhood. Clinical examination confirmed retinopathy resembling Stargardt disease. Electroretinography revealed cone-rod dysfunction. Whole exome sequencing with attention to ABCA4 was unrevealing for retinal dystrophy genes but did uncover a homozygous GAS8 deletion, molecularly confirming the diagnosis of primary ciliary dyskinesia. Literature review revealed a report of a 34-year-old North African male with GAS8-related primary ciliary dyskinesia who also had been diagnosed with Stargardt disease in the absence of pathogenic ABCA4 variants. DISCUSSION: Longer follow-up of individuals with primary ciliary dyskinesia may reveal findings more typically associated with non-motile ciliopathy such as retinal dystrophy. GAS8-related retinal dystrophy can resemble Stargardt disease.

Phenotypes and genotypes underlying paradoxical pupillary reaction in children.

Paradoxical pupillary reaction (initial pupillary constriction to darkness) has been most associated with the inherited retinal disorders congenital stationary night blindness and achromatopsia. However, underlying genotypes and associations with other pediatric retinal phenotypes are not well documented. A retrospective review for paradoxical pupillary reaction was performed at the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi (2016-2020). Four children from 4 different families were identified, all of whom had had genetic confirmation of the clinical diagnosis. Associated pathogenic variants were in TRPM1 (biallelic; two boys; congenital stationary night blindness), CABP4 (biallelic; one boy, congenital cone-rod synaptic disorder) and PAX2 (monoallelic; one girl, papillorenal syndrome). Genetically confirmed affected relatives of the 2 probands with TRPM1-related congenital stationary night blindness did not show the phenomenon. This study documents novel genotypes and phenotypes that can be associated with paradoxical pupillary reaction in children and confirms potential intrafamilial variable expressivity for the phenomenon.

Loss of the collagen IV modifier prolyl 3-hydroxylase 2 causes thin basement membrane nephropathy.

The glomerular filtration barrier (GFB) produces primary urine and is composed of a fenestrated endothelium, a glomerular basement membrane (GBM), podocytes, and a slit diaphragm. Impairment of the GFB leads to albuminuria and microhematuria. The GBM is generated via secreted proteins from both endothelial cells and podocytes and is supposed to majorly contribute to filtration selectivity. While genetic mutations or variations of GBM components have been recently proposed to be a common cause of glomerular diseases, pathways modifying and stabilizing the GBM remain incompletely understood. Here, we identified prolyl 3-hydroxylase 2 (P3H2) as a regulator of the GBM in an a cohort of patients with albuminuria. P3H2 hydroxylates the 3' of prolines in collagen IV subchains in the endoplasmic reticulum. Characterization of a P3h2ΔPod mouse line revealed that the absence of P3H2 protein in podocytes induced a thin basement membrane nephropathy (TBMN) phenotype with a thinner GBM than that in WT mice and the development of microhematuria and microalbuminuria over time. Mechanistically, differential quantitative proteomics of the GBM identified a significant decrease in the abundance of collagen IV subchains and their interaction partners in P3h2ΔPod mice. To our knowledge, P3H2 protein is the first identified GBM modifier, and loss or mutation of P3H2 causes TBMN and focal segmental glomerulosclerosis in mice and humans.

Adult-onset bestrophinopathy mistaken as central serous chorioretinopathy.

PURPOSE: To highlight cases of adult-onset bestrophinopathy mistaken as central serous chorioretinopathy (CSCR). METHODS: Retrospective case series. RESULTS: Two unrelated adult males (54 years old and 43 years old) with serous macular detachments were managed as CSCR. One had been treated with intraocular injections and oral mineralcorticoid inhibitors. Independently, each had an 8-year-old son who presented with classic Best disease, which raised suspicion for bestrophinopathy in their fathers. Bestrophin sequencing confirmed each son to be heterozygous for a pathogenic variant, and targeted testing confirmed each respective father to harbor the same heterozygous pathogenic variant as his son. Electro-oculography of the first father-son pair confirmed decreased Arden ratios. Review of multimodal imaging of the adult patients revealed a hyper-autofluorescent edge surrounding a serous macular detachment by short-wave autofluorescence and shaggy photoreceptors on the overlying edge of serous detachments by optical coherence tomography. DISCUSSION: Adult-onset bestrophinopathy can be mistaken as CSCR. Multimodal imaging findings, examination of potentially affected family members, electrophysiology, and genetic testing facilitate the correct diagnosis.