A Description of the Yield of Genetic Reinvestigation in Patients with Inherited Retinal Dystrophies and Previous Inconclusive Genetic Testing.

In the present era of evolving gene-based therapies for inherited retinal dystrophies (IRDs), it has become increasingly important to verify the genotype in every case, to identify all subjects eligible for treatment. Moreover, combined insight concerning phenotypes and genotypes is crucial for improved understanding of thevisual impairment, prognosis, and inheritance. The objective of this study was to investigate to what extent renewed comprehensive genetic testing of patients diagnosed with IRD but with previously inconclusive DNA test results can verify the genotype, if confirmation of the genotype has an impact on the understanding of the clinical picture, and, to describe the genetic spectrum encountered in a Swedish IRD cohort. The study included 279 patients from the retinitis pigmentosa research registry (comprising diagnosis within the whole IRD spectrum), hosted at the Department of Ophthalmology, Skåne University hospital, Sweden. The phenotypes had already been evaluated with electrophysiology and other clinical tests, e.g., visual acuity, Goldmann perimetry, and fundus imaging at the first visit, sometime between 1988-2015 and the previous-in many cases, multiple-genetic testing, performed between 1995 and 2020 had been inconclusive. All patients were aged 0-25 years at the time of their first visit. Renewed genetic testing was performed using a next generation sequencing (NGS) IRD panel including 322 genes (Blueprint Genetics). Class 5 and 4 variants, according to ACMG guidelines, were considered pathogenic. Of the 279 samples tested, a confirmed genotype was determined in 182 (65%). The cohort was genetically heterogenous, including 65 different genes. The most prevailing were ABCA4 (16.5%), RPGR (6%), CEP290 (6%), and RS1 (5.5%). Other prevalent genes were CACNA1F (3%), PROM1 (3%), CHM (3%), and NYX (3%). In 7% of the patients there was a discrepancy between the diagnosis made based on phenotypical or genotypical findings alone. To conclude, repeated DNA-analysis was beneficial also in previously tested patients and improved our ability to verify the genotype-phenotype association increasing the understanding of how visual impairment manifests, prognosis, and the inheritance pattern. Moreover, repeated testing using a widely available method could identify additional patients eligible for future gene-based therapies.

Cost-effective sequence analysis of 113 genes in 1,192 probands with retinitis pigmentosa and Leber congenital amaurosis.

Introduction: Retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA) are two groups of inherited retinal diseases (IRDs) where the rod photoreceptors degenerate followed by the cone photoreceptors of the retina. A genetic diagnosis for IRDs is challenging since >280 genes are associated with these conditions. While whole exome sequencing (WES) is commonly used by diagnostic facilities, the costs and required infrastructure prevent its global applicability. Previous studies have shown the cost-effectiveness of sequence analysis using single molecule Molecular Inversion Probes (smMIPs) in a cohort of patients diagnosed with Stargardt disease and other maculopathies. Methods: Here, we introduce a smMIPs panel that targets the exons and splice sites of all currently known genes associated with RP and LCA, the entire RPE65 gene, known causative deep-intronic variants leading to pseudo-exons, and part of the RP17 region associated with autosomal dominant RP, by using a total of 16,812 smMIPs. The RP-LCA smMIPs panel was used to screen 1,192 probands from an international cohort of predominantly RP and LCA cases. Results and discussion: After genetic analysis, a diagnostic yield of 56% was obtained which is on par with results from WES analysis. The effectiveness and the reduced costs compared to WES renders the RP-LCA smMIPs panel a competitive approach to provide IRD patients with a genetic diagnosis, especially in countries with restricted access to genetic testing.

A five-year follow-up of ABCA4 carriers showing deterioration of retinal function and increased structural changes.

Purpose: To investigate whether the reduced retinal function and morphological retinal changes previously demonstrated in ABCA4 carriers had remained stationary or had deteriorated over time at 5-year follow-up to further explore if carriers of an autosomal recessive trait also express a weak phenotype, although this is not expected for an autosomal recessive disorder. Methods: Thirteen ABCA4 carriers from a previous study that included parents to patients with well known genetically verified ABCA4-associated retinal degenerations were reexamined 5 years after the initial examination. As novel genes and new variants in already established genes are continuously reported, all subjects underwent renewed genetic testing with a next-generation sequencing (NGS) panel that included 288 genes associated with retinal dystrophies and an analysis of deep intronic mutations and copy number variations in the ABCA4 gene. Moreover, to evaluate any changes in retinal function and/or structure over time, clinical reassessment with Goldmann perimetry, visual acuity testing, fundus photography, fundus autofluorescence (FAF) imaging, optical coherence tomography (OCT), full-field electroretinography (ffERG), and multifocal ERG (mfERG) were performed 5 years after the initial investigation. The values of the ffERG parameters were compared between the two time points (the measurements obtained in the initial study versus the measurements at 5-year follow-up) and with the controls. The mfERG results of the carriers were compared with those of the controls. Results: The renewed genetic testing confirmed the previously established ABCA4 mutations but also revealed the hypomorph ABCA4 variant c.5603A>T in five ABCA4 carriers. In three of them, the variant was found to be associated with known disease-causing alleles that always carry the c.5603A>T in cis. According to recent publications, the subjects could still be considered ABCA4 carriers because both variants are on the same allele. In the remaining two subjects, c.5603A>T could be in trans with the previously known ABCA4 variant, and the subjects were therefore excluded from the study since they could no longer be considered as carriers only. Statistical comparison of ffERG parameters showed significant reduction of the isolated rod, -as well as the combined rod-cone amplitudes over the five years of follow-up, but not compared with the controls. Concerning macular function, mfERG amplitudes were reduced for all rings in the carriers compared with the controls. Fundus photographs demonstrated morphological changes in 64% of the carriers, and 36% of them had further changes at follow-up. FAF images showed alterations in 55% of the carriers, with increased changes in 36% of them. Abnormalities on OCT were observed in 82% of the carriers, of whom 9% had newly found abnormalities at follow-up. Conclusions: At 5-year follow-up, the ABCA4 carriers, who previously demonstrated reduced macular function, presented with deterioration of general retinal function, including reduced isolated rod and mixed rod-cone ffERG responses combined with a slight increase in morphological changes in some subjects. This indicates that carriership of at least some ABCA4 variants may cause a condition similar to a subgroup of dry age-related macular degeneration (AMD). In the long run, this might be of importance concerning the possibilities to also treat this subgroup of AMD patients with future gene-based and pharmacological drugs targeting ABCA4-associated disorders.

The landscape of submicroscopic structural variants at the OPN1LW/OPN1MW gene cluster on Xq28 underlying blue cone monochromacy.

Blue cone monochromacy (BCM) is an X-linked retinal disorder characterized by low vision, photoaversion, and poor color discrimination. BCM is due to the lack of long-wavelength-sensitive and middle-wavelength-sensitive cone photoreceptor function and caused by mutations in the OPN1LW/OPN1MW gene cluster on Xq28. Here, we investigated the prevalence and the landscape of submicroscopic structural variants (SVs) at single-base resolution in BCM patients. We found that about one-third (n = 73) of the 213 molecularly confirmed BCM families carry an SV, most commonly deletions restricted to the OPN1LW/OPN1MW gene cluster. The structure and precise breakpoints of the SVs were resolved in all but one of the 73 families. Twenty-two families-all from the United States-showed the same SV, and we confirmed a common ancestry of this mutation. In total, 42 distinct SVs were identified, including 40 previously unreported SVs, thereby quadrupling the number of precisely mapped SVs underlying BCM. Notably, there was no "region of overlap" among these SVs. However, 90% of SVs encompass the upstream locus control region, an essential enhancer element. Its minimal functional extent based on deletion mapping in patients was refined to 358 bp. Breakpoint analyses suggest diverse mechanisms underlying SV formation as well as in one case the gene conversion-based exchange of a 142-bp deletion between opsin genes. Using parsimonious assumptions, we reconstructed the composition and copy number of the OPN1LW/OPN1MW gene cluster prior to the mutation event and found evidence that large gene arrays may be predisposed to the occurrence of SVs at this locus.

A novel phenotype associated with the R162W variant in the KCNJ13 gene.

BACKGROUND: Pathogenic variants in KCNJ13 have been associated with both autosomal dominant Snowflake vitreoretinal degeneration (SVD) and autosomal recessive Leber congenital amaurosis. SVD is characterized by aberrant vitreoretinal interface leading to increased risk of retinal detachment, crystalline retinal snowflake deposits, optic disc abnormalities, early-onset cataract, and cornea guttae. Reduced dark adaptation and reduced scotopic rod b-waves have also been described. We report a novel phenotype associated with the R162W variant in KCNJ13. METHODS: Four affected members of a Swedish family were included. Three of them were examined with best corrected visual acuity, Goldmann perimetry, full-field-and multifocal electroretinography, optical coherence tomography, fundus color photographs, fundus autofluorescence images, slit lamp inspection, and genetic testing. The fourth subject only managed genetic testing. RESULTS: All subjects carry the pathogenic missense variant; c.484C>T (NM_002242.4), R162W, in KCNJ13. ERG measurements revealed reduced macular-as well as general retinal function. Two of the subjects had a history of retinal detachment and the two younger subjects demonstrated early onset cataract. They all had structural macular changes and slightly gliotic optic discs. CONCLUSION: In this family, the R162W variant in KCNJ13, previously described in association with SVD, causes a somewhat novel phenotype including macular dystrophy and moderate reduction of general retinal function as the main features combined with disc abnormalities, retinal detachment, and presenile cataract that has been described before. In times of up-coming gene-based therapies, it is important to report new genotype-phenotype associations to improve the possibilities to identify future treatment candidates.

Comprehensive variant spectrum of the CNGA3 gene in patients affected by achromatopsia.

Achromatopsia (ACHM) is a congenital cone photoreceptor disorder characterized by impaired color discrimination, low visual acuity, photosensitivity, and nystagmus. To date, six genes have been associated with ACHM (CNGA3, CNGB3, GNAT2, PDE6C, PDE6H, and ATF6), the majority of these being implicated in the cone phototransduction cascade. CNGA3 encodes the CNGA3 subunit of the cyclic nucleotide-gated ion channel in cone photoreceptors and is one of the major disease-associated genes for ACHM. Herein, we provide a comprehensive overview of the CNGA3 variant spectrum in a cohort of 1060 genetically confirmed ACHM patients, 385 (36.3%) of these carrying "likely disease-causing" variants in CNGA3. Compiling our own genetic data with those reported in the literature and in public databases, we further extend the CNGA3 variant spectrum to a total of 316 variants, 244 of which we interpreted as "likely disease-causing" according to ACMG/AMP criteria. We report 48 novel "likely disease-causing" variants, 24 of which are missense substitutions underlining the predominant role of this mutation class in the CNGA3 variant spectrum. In addition, we provide extensive in silico analyses and summarize reported functional data of previously analyzed missense, nonsense and splicing variants to further advance the pathogenicity assessment of the identified variants.

Full-Field Electroretinography Changes Associated with Age-Related Macular Degeneration: A Systematic Review with Meta-Analyses.

BACKGROUND: The aim of this study was to systematically review the literature and to perform meta-analyses on full-field electroretinography (ffERG) between healthy controls and age-related macular degeneration (AMD) to map the extent of retinal dysfunction. SUMMARY: We systematically searched 11 databases on 3 March 2021. Eligible studies had to measure retinal function using ffERG in eyes with AMD and in healthy controls. We extracted data on a-wave and b-wave function in dark- and light-adapted ffERG and calculated summary estimates on differences between eyes with AMD and controls using weighted mean differences (WMD). Subgroup analyses were made for early and late AMD. Six studies (n = 481 eyes) were eligible for review (301 with any AMD, 180 controls). For dark-adapted data, any AMD was associated with reduced a-wave amplitude (WMD: -17.16 µV; 95% CI: -31.79 to -2.52 µV; p = 0.02) and b-wave amplitude (WMD: -28.70 µV; 95% CI: -51.40 to -6.01 µV; p = 0.01). For light-adapted data, any AMD was associated with longer a-wave implicit time (WMD: 0.92 ms; 95% CI: 0.12-1.72 ms; p = 0.02), reduced b-wave amplitude (WMD: -13.26 µV; 95% CI: -18.64 to -7.88 µV; p < 0.0001), and longer b-wave implicit time (WMD: 0.69 ms; 95% CI: 0.30-1.08 ms; p = 0.0006). Subgroup analyses found that these changes were only statistically significant in eyes with late AMD, not early AMD. KEY MESSAGES: Reduced retinal function on ffERG is present in eyes with AMD, in particular those with late AMD. These findings suggest that AMD is a pan-retinal disease with AMD-associated photoreceptor dysfunction beyond the macula.

Full-field electroretinography in age-related macular degeneration: an overall retinal response.

PURPOSE: Age-related macular degeneration (AMD) is generally considered a disease of the macula. However, recent studies show peripheral retinal lesions are prevalent in patients with AMD, indicative of a disease process that is more widespread. Full-field electroretinography (ffERG) measures an electrical response, not only from the macula, but from the entire retina. We wanted to study the ffERG response in eyes with AMD. METHODS: We performed full-field electroretinography (RETI-port/scan 21, Roland, Berlin) in 13 patients with early AMD, 25 patients with late AMD and 24 individuals without vitreoretinal disease as a control group. Dawson-Trick-Litzkow fibre electrodes were used. Statistical analysis was performed and a p-value <0.05 was considered significant. RESULTS: After adjusting for multiple comparisons, both the light-adapted 3.0 a-wave implicit time (p < 0.001) and 30-Hertz flicker peak time (p = 0.012) showed significant difference between patients with late AMD and individuals without vitreoretinal disease. There was a significant difference in the light-adapted 3.0 a-wave implicit time (p = 0.011) between patients with early AMD and the control group, but the difference in 30 Hz flicker peak time was not significant (p = 0.256). CONCLUSION: The difference in cone function measured by light-adapted 3.0 a-wave implicit time and 30-Hertz flicker peak time in early and late AMD when compared to healthy controls suggests a more diminished overall response when AMD has reached later stages.

Autosomal recessive Stickler syndrome associated with homozygous mutations in the COL9A2 gene.

Background: Stickler syndrome is a hereditary disorder of collagen tissues causing ocular, auditory, orofacial, and joint manifestations. Ocular findings typically include vitreous degeneration, high myopia, retinal detachment, and cataract. Many subjects demonstrate sensorineural or conductive hearing loss. The inheritance is autosomal dominant with mutations in COL2A1, COL11A1, or COL11A2 or autosomal recessive due to mutations in COL9A1, COL9A2, or COL9A3. We describe a family with Stickler syndrome caused by homozygous loss-of-function mutations in COL9A2.Methods: Two brothers from a consanguineous family were examined with genetic testing, visual acuity, Goldmann perimetry, full-field and multifocal electroretinography (ffERG, mERG), optical coherence tomography (OCT), fundus autofluorescence (FAF), fundus photography, and pure-tone audiograms.Results: Both subjects were homozygous for the mutation c.1332del in COL9A2. Their parents were heterozygous for the same mutation. The boys demonstrated reduced visual acuity, vitreous changes and myopia. The proband was operated for retinal detachment and cataract in one eye. FfERG revealed reduced function of both rods and cones and mERG showed reduced macular function. No morphological macular changes were found by OCT or FAF. Both brothers have severe sensorineural hearing loss with down-sloping audiograms but only subtle midface hypoplasia and no, or mild joint problems.Conclusion: Only a few families with Stickler syndrome caused by COL9A2 mutations have been reported. We confirm previous descriptions with a severe ocular and auditory phenotype but mild orofacial and joint manifestations. Moreover, we demonstrate reduced macular and overall retinal function explaining the reduced visual acuity in patients with Stickler syndrome also without retinal complications.

Clinical Phenotype and Course of PDE6A-Associated Retinitis Pigmentosa Disease, Characterized in Preparation for a Gene Supplementation Trial.

Importance: Treatment trials require sound knowledge on the natural course of disease. Objective: To assess clinical features, genetic findings, and genotype-phenotype correlations in patients with retinitis pigmentosa (RP) associated with biallelic sequence variations in the PDE6A gene in preparation for a gene supplementation trial. Design, Setting, and Participants: This prospective, longitudinal, observational cohort study was conducted from January 2001 to December 2019 in a single center (Centre for Ophthalmology of the University of Tübingen, Germany) with patients recruited multinationally from 12 collaborating European tertiary referral centers. Patients with retinitis pigmentosa, sequence variants in PDE6A, and the ability to provide informed consent were included. Exposures: Comprehensive ophthalmological examinations; validation of compound heterozygosity and biallelism by familial segregation analysis, allelic cloning, or assessment of next-generation sequencing-read data, where possible. Main Outcomes and Measures: Genetic findings and clinical features describing the entire cohort and comparing patients harboring the 2 most common disease-causing variants in a homozygous state (c.304C>A;p.(R102S) and c.998 + 1G>A;p.?). Results: Fifty-seven patients (32 female patients [56%]; mean [SD], 40 [14] years) from 44 families were included. All patients completed the study. Thirty patients were homozygous for disease-causing alleles. Twenty-seven patients were heterozygous for 2 different PDE6A variants each. The most frequently observed alleles were c.304C>A;p.(R102S), c.998 + 1G>A;p.?, and c.2053G>A;p.(V685M). The mean (SD) best-corrected visual acuity was 0.43 (0.48) logMAR (Snellen equivalent, 20/50). The median visual field area with object III4e was 660 square degrees (5th and 95th percentiles, 76 and 11 019 square degrees; 25th and 75th percentiles, 255 and 3923 square degrees). Dark-adapted and light-adapted full-field electroretinography showed no responses in 88 of 108 eyes (81.5%). Sixty-nine of 108 eyes (62.9%) showed additional findings on optical coherence tomography imaging (eg, cystoid macular edema or macular atrophy). The variant c.998 + 1G>A;p.? led to a more severe phenotype when compared with the variant c.304C>A;p.(R102S). Conclusions and Relevance: Seventeen of the PDE6A variants found in these patients appeared to be novel. Regarding the clinical findings, disease was highly symmetrical between the right and left eyes and visual impairment was mild or moderate in 90% of patients, providing a window of opportunity for gene therapy.

Longitudinal Changes of Macular Curvature in Patients with Retinitis Pigmentosa.

Purpose: To investigate the longitudinal changes of the macular curvature in eyes with retinitis pigmentosa (RP) and to determine the factors associated with the changes. Methods: We reviewed the medical charts of 107 RP patients, for whom the axial length of their right eyes ranged from 21.5 to 26.0 mm and who had had been followed by spectral-domain optical coherence tomography (OCT). The OCT images at the initial and the most recent examinations were compared. The mean curvature of Bruch's membrane within 6 mm of the central macula obtained from the OCT images was evaluated as the mean macular curvature index (MMCI). Changes in the MMCI and their relationships with other clinical factors, including the ellipsoid zone (EZ) width, were assessed. Results: The MMCI decreased significantly in the vertical OCT images, from -15.47 × 10-5 µm-1 to -16.36 × 10-5 µm-1 (P = 0.008) during the mean observation period of 3.4 ± 1.4 years (mean ± SD). This indicated that the macular shape became more concave. The change to a steeper shape was more prominent in eyes with less photoreceptor degeneration and for which the EZ width was preserved at >2000 µm. In three eyes, the MMCI increased markedly by >5 × 10-5 µm-1, and this was accompanied by absorption of the macular edema. Conclusions: The macular curvature in RP eyes becomes more concave in eyes with preserved EZ width. Translational Relevance: Longitudinal changes of the macular curvature in RP should be considered in future therapies, such as the implantation of the retinal prosthesis.

Long-term effects of hyperbaric oxygen therapy on visual acuity and retinopathy.

Hyperbaric oxygen (HBO2) therapy is an adjunct treatment for diabetic foot ulcers. Since plausible mechanisms of action for this treatment include increased angiogenesis and high tissue oxygen concentrations, concerns about deterioration of retinopathy have been raised. The aim of this study was to evaluate the effects of HBO2 on visual acuity (VA) and retinopathy in patients with chronic diabetic foot ulcers during a two-year follow-up period. This is a randomized, single-center, double-blinded and placebo-controlled clinical trial evaluating the effects of HBO2 in patients with diabetes mellitus and chronic foot ulcers. All study participants underwent an ophthalmological examination before the first study treatment and then at three, six, 12 and 24 months. Fifty patients with a median age of 67 years were included. Visual acuity was similar between groups and did not change during the two-year observation period. No differences in retinopathy were seen between groups; neither were any differences found in numbers or areas of bleedings, hard exudates, microaneurysms or edemas, nor between groups or visits. New clinically significant macular edema was identified in four eyes in the HBO2 group and in three eyes in the placebo group. In this population of diabetic foot ulcer patients HBO2 seems to be neutral in an ophthalmological perspective. From a retinal point of view, we could not identify any indication of harmful effects of HBO2 on the microvascular bed in the placebo group.

Full-field Electroretinography in Age-related Macular Degeneration: can retinal electrophysiology predict the subjective visual outcome of cataract surgery?

PURPOSE: Predicting the visual gain from cataract surgery when the main cause of vision loss is age-related macular degeneration may be difficult and warrants the need for an objective predictor of subjective outcome. Full-field electroretinography is an objective measure of overall retinal function. We therefore wanted to study if full-field electroretinography can predict subjective visual outcome using visual function questionnaire. METHODS: Thirty-one patients with age-related macular degeneration operated for bilateral cataract underwent full-field electroretinography preoperatively. Full-field electroretinography was performed according to International Society for the Clinical Electrophysiology of Vision standards using a Ganzfeld bowl (RETI-port/scan 21, Roland, Berlin) and Dawson-Trick-Litzkow fibre electrodes. Vision-related quality of life was measured using the National Eye Institute Visual Function Questionnaire-39 before first-eye surgery and 4.12 ± 2.11 months after second-eye surgery. RESULTS: Mean change in composite visual function questionnaire score after cataract surgery was 9.2 ± 11.9. The patients were divided into three groups: visual function questionnaire composite score increase >10 (n = 17); no change (n = 8); and decrease (n = 6). In the dark-adapted full-field electroretinography responses, we found a significant difference between the three groups in the 0.01 b-wave amplitude (p = 0.05), the 10.0 b-wave amplitude (p = 0.04) and a near-significant difference in 3.0 a-wave amplitude (p = 0.09). Other dark-adapted responses (the 3.0 b-wave and 10.0 a-wave) did not show any significant differences between the three groups, and neither did the light-adapted responses. CONCLUSION: Patients with low dark-adapted responses on full-field electroretinography preoperatively experience a decrease in subjective vision-related quality of life, suggesting that maintained rod function before cataract surgery may be important.

A novel missense variant in IDH3A causes autosomal recessive retinitis pigmentosa.

BACKGROUND: Inherited retinal degenerations (IRDs) encompass a wide spectrum of genetic ocular diseases characterized by considerable genetic and clinical heterogeneity. METHODS: Complete ophthalmic examination and next-generation sequencing. RESULTS: We describe a patient with no family history of vision loss, who at the age of 28 years developed visual impairment consistent with a severe form of retinitis pigmentosa. Genetic testing by means of whole exome sequencing identified a homozygous variant in the gene IDH3A. To date, only three papers have reported mutations in IDH3A, in families with early-onset retinal degeneration with or without the presence of macular pseudocoloboma. CONCLUSION: This study highlights the importance of including this rarely-mutated gene in the molecular diagnostic set-ups for IRDs, and further delineates the phenotypic spectrum elicited by mutations in IDH3A.

Cerebral Functional Magnetic Resonance Imaging and Multifocal Visual Evoked Potentials in a Patient with Unexplained Impairment of Visual Function: A Case Report.

We present a case of a young female with a slowly progressing visual impairment who was examined with multifocal visual evoked potentials and functional magnetic resonance imaging (fMRI) for underlying neuronal abnormality. The fMRI examination consisted of presenting black-and-white checkerboard stimuli, and her activation patterns were compared to the patterns from 4 normal-sighted subjects. The results showed clear differences in neuronal activation between the patient and the controls in the occipital and parietal lobes. Although we have shown neuronal correlates in a case of unexplained visual loss, it is still an open question as to whether this has an organic or functional cause, which should be the subject for future research.

An Expanded Multi-Organ Disease Phenotype Associated with Mutations in YARS.

Whole exome sequence analysis was performed in a Swedish mother-father-affected proband trio with a phenotype characterized by progressive retinal degeneration with congenital nystagmus, profound congenital hearing impairment, primary amenorrhea, agenesis of the corpus callosum, and liver disease. A homozygous variant c.806T > C, p.(F269S) in the tyrosyl-tRNA synthetase gene (YARS) was the only identified candidate variant consistent with autosomal recessive inheritance. Mutations in YARS have previously been associated with both autosomal dominant Charcot-Marie-Tooth syndrome and a recently reported autosomal recessive multiorgan disease. Herein, we propose that mutations in YARS underlie another clinical phenotype adding a second variant of the disease, including retinitis pigmentosa and deafness, to the spectrum of YARS-associated disorders.

Ataxia-pancytopenia syndrome with SAMD9L mutations.

OBJECTIVE: We describe the neurologic, neuroradiologic, and ophthalmologic phenotype of 1 Swedish and 1 Finnish family with autosomal dominant ataxia-pancytopenia (ATXPC) syndrome and SAMD9L mutations. METHODS: Members of these families with germline SAMD9L c.2956C>T, p.Arg986Cys, or c.2672T>C, p.Ile891Thr mutations underwent structured interviews and neurologic and ophthalmologic examinations. Neuroimaging was performed, and medical records were reviewed. Previous publications on SAMD9L-ATXPC were reviewed. RESULTS: Twelve individuals in both families were affected clinically. All mutation carriers examined had balance impairment, although severity was very variable. All but 1 had nystagmus, and all but 1 had pyramidal tract signs. Neurologic features were generally present from childhood on and progressed slowly. Two adult patients, who experienced increasing clumsiness, glare, and difficulties with gaze fixation, had paracentral retinal dysfunction verified by multifocal electroretinography. Brain MRI showed early, marked cerebellar atrophy in most carriers and variable cerebral periventricular white matter T2 hyperintensities. Two children were treated with hematopoietic stem cell transplantation for hematologic malignancies, and the neurologic symptoms of one of these worsened after treatment. Three affected individuals had attention deficit hyperactivity disorder or cognitive problems. Retinal dysfunction was not previously reported in individuals with ATXPC. CONCLUSIONS: The neurologic phenotype of this syndrome is defined by balance or gait impairment, nystagmus, hyperreflexia in the lower limbs and, frequently, marked cerebellar atrophy. Paracentral retinal dysfunction may contribute to glare, reading problems, and clumsiness. Timely diagnosis of ATXPC is important to address the risk for severe hemorrhage, infection, and hematologic malignancies inherent in this syndrome; regular hematologic follow-up might be beneficial.