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.

The genetic basis of clinically-suspected achromatopsia in the United Arab Emirates.

PURPOSE: Achromatopsia (ACHM) is a genetically heterogenous relatively stationary congenital autosomal recessive cone disorder characterized typically by photophobia, low vision, nystagmus, hyperopia, grossly normal retinal appearance, and absent photopic responses by full-field electroretinography. Incomplete forms occur as well. This study investigates the genetic basis of clinically-suspected ACHM in the United Arab Emirates. METHODS: Retrospective case series (January 2016-December 2023) of patients with (1) clinically-suspected ACHM and (2) mutations in ACHM-associated genes (CNGA3, CNGB3, GNAT2, PDE6C, PDE6H, AT6). RESULTS: Twenty-two clinically-suspected patients (19 probands) were identified. Biallelic disease genes and number of probands were CNGA3 (9), CNGB3 (6), PDE6C (1), GNAT2 (1), RGS9BP (1), and CNNM4 (1). Two probands had their diagnoses revised after genetic testing and phenotypic reassessment to RGS9BP-related bradyopsia and CNNM4-related Jalili syndrome. Three additional cases (making 22 total probands) were identified from ACHM gene mutation review - one each related to PDE6C, to AT6, and to CNGB3 in concert with CNGA3 (triallelic disease). All three presented with macular discoloration, an atypical finding for classic ACHM. CONCLUSION: CNGA3 was the single most frequent implicated gene. Bradyopsia and Jalili syndrome can resemble incomplete ACHM. Macular discoloration on presentation can occur in PDE6C-related disease, AT6-related disease, and triallelic CNGB3/CNGA3-related disease. The possibility for triallelic disease exists and requires genetic counseling beyond that of simple autosomal recessive inheritance.

Usher syndrome in the United Arab Emirates.

PURPOSE: Usher syndrome, a common form of syndromic inherited retinal dystrophy in the Arabian Gulf, has not been molecularly defined in the United Arab Emirates. The current study addresses this gap in knowledge. METHODS: A retrospective case series of Emirati patients referred to the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi who (1) were clinically diagnosed with Usher syndrome and underwent genetic testing (whole exome sequencing, 2019 to 2023, inclusive) and (2) were identified to have biallelic pathogenic variants in Usher syndrome genes during the same time period. RESULTS: Ten probands (thirteen patients) were identified-seven probands (nine patients) with clinically diagnosed Usher syndrome and three additional probands (four patients) with biallelic homozygous USH2A variants. Among the seven probands initially diagnosed with Usher syndrome, six had different homozygous variants (three in MYO7A, one in ADGRV1, and one in CLRN1), one had dual diagnoses rather than Usher syndrome (i.e. separate cause for retinal dystrophy and deafness), and one had no identifiable genetic cause. Regarding the three additional probands identified with homozygous USH2A variants, all three had retinitis pigmentosa only rather than Usher syndrome and all three had different variants. DISCUSSION: Clinically diagnosed Usher syndrome was genetically heterogenous without evidence for founder effect in this Emirati cohort. MYO7A was the most common associated gene. Dual diagnosis rather than single cause can mimic Usher syndrome. Homozygous USH2A variants were not identified as a cause for Usher syndrome in this cohort but were a recurrent cause for retinitis pigmentosa without hearing impairment and without founder effect.

Biallelic occult macular dystrophy.

PURPOSE: Occult macular dystrophy (OMD) is a cause of visual loss in young adults with a grossly normal fundus appearance. It is considered an autosomal dominant disorder, related to heterozygous pathogenic variants in the gene RP1L1. The purpose of this study is to report a biallelic form of the disease. RESULTS: A 29-year-old female had undergone neurological workup and ophthalmic examinations for transient visual loss in her left eye over the past two years but there was no definitive diagnosis. The best-corrected visual acuity was 20/30, 20/20. Indirect ophthalmoscopy with a 78D lens revealed subtle central retinal pigment epithelium mottling and optical coherence tomography confirmed subtle central thickening of the ellipsoid zone. Full-field electroretinography was normal, but pattern electroretinography showed decreased p50 responses. OMD was suspected. Retinal gene panel testing was significant only for a homozygous variant in RP1L1 (NM_178857.6: c.3571 G>T; p.Glu1191*). The parents and older brother were unavailable for segregation analysis. By history they did not have visual complaints other than a need for glasses. CONCLUSIONS: This report presents the clinical and genetic findings of a biallelic form of OMD associated with a novel pathogenic variant in RP1L1. It would be of interest to carefully assess macular function in heterozygotes with this variant.

Paradoxical keratitis and dermatitis following adalimumab treatment.

Anti-tumor necrosis factor monoclonal antibodies are an important tool in the management of rheumatologic disease. However, paradoxical inflammation can be precipitated by their use. This case report describes the development of keratitis and dermatitis following adalimumab treatment for chronic recurrent multifocal osteomyelitis in a 6-year-old girl. The keratitis and dermatitis subsided once topical steroids were started and the adalimumab was held.

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.

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.

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.