Metabolomics facilitates differential diagnosis in common inherited retinal degenerations by exploring their profiles of serum metabolites.

The diagnosis of inherited retinal degeneration (IRD) is challenging owing to its phenotypic and genotypic complexity. Clinical information is important before a genetic diagnosis is made. Metabolomics studies the entire picture of bioproducts, which are determined using genetic codes and biological reactions. We demonstrated that the common diagnoses of IRD, including retinitis pigmentosa (RP), cone-rod dystrophy (CRD), Stargardt disease (STGD), and Bietti's crystalline dystrophy (BCD), could be differentiated based on their metabolite heatmaps. Hundreds of metabolites were identified in the volcano plot compared with that of the control group in every IRD except BCD, considered as potential diagnosing markers. The phenotypes of CRD and STGD overlapped but could be differentiated by their metabolomic features with the assistance of a machine learning model with 100% accuracy. Moreover, EYS-, USH2A-associated, and other RP, sharing considerable similar characteristics in clinical findings, could also be diagnosed using the machine learning model with 85.7% accuracy. Further study would be needed to validate the results in an external dataset. By incorporating mass spectrometry and machine learning, a metabolomics-based diagnostic workflow for the clinical and molecular diagnoses of IRD was proposed in our study.

Correlation between neutrophil-to-lymphocyte ratio and clinical manifestations and complications of retinitis pigmentosa.

PURPOSE: The role of inflammation in retinitis pigmentosa (RP) has been receiving additional attention. However, the association between inflammation and the clinical manifestations and complications of RP is still unclear. This study aimed to evaluate the neutrophil-to-lymphocyte ratio (NLR) of RP complicated with cataract and explore the correlations between the NLR and specific clinical features of RP. METHODS: This retrospective study included 79 RP patients complicated with cataract (125 eyes) and 63 age- and sex-matched patients (63 eyes) with age-related cataract (ARC). Patients' ocular examination results were collected and complete blood count results were used to calculate NLRs. The correlations between the NLR of RP patients and the parameters of ocular examinations were analysed. RESULTS: The NLRs of RP patients with cataracts were significantly higher than those of ARC (1.93 ± 0.83 versus 1.65 ± 0.59, p = 0.029). The NLRs increased with the severity of posterior subcapsular cataract (PSC), zonular deficiency, poor preoperative best-corrected visual acuity (LogMAR>1), and visual field defects. Analysis of receiver operating characteristic curves suggested that NLR > 1.36 could predict higher degrees (PSC area >3%, >P1) of PSC (p = 0.002, 95% CI, 0.672-0.934), and that NLR > 2.12 could predict zonular weakness (p = 0.002, 95% CI, 0.665-0.928) in RP. CONCLUSION: The NLRs in RP patients with cataract are not only higher but also associated with several clinical manifestations of RP. The NLR can be a predictive biomarker of higher degrees of PSC (>P1) and zonular weakness in RP before cataract surgery. These results suggest that systemic inflammation may play a role in the pathogenesis of RP.

Thiol/disulfide homeostasis in retinitis pigmentosa patients.

PURPOSE: This research is aimed at determination of total oxidant status, total antioxidant status, serum thiol-disulfide, catalase, albumin, ischemia-modified albumin, and ceruloplasmin in patients suffering from retinitis pigmentosa and drawing a comparison with these parameters determined from healthy controls. METHODS: The study involved 35 patients of retinitis pigmentosa and 33 controls who were healthy individuals of comparable gender and age. Native thiol, total thiol, disulfide concentration, disulfide/native thiol, disulfide/total thiol, native thiol/total thiol ratios, total oxidant status, total antioxidant status, catalase, ceruloplasmin, albumin, and ischemia-modified albumin were determined from peripheral blood samples and comparison was drawn between the measurements of retinitis pigmentosa and controls. RESULTS: The two groups were similar in gender and age distributions. It was found that retinitis pigmentosa group demonstrated greater total oxidant status, ischemia-modified albumin, and disulfide concentrations as compared to controls (p < 0.001). However, total antioxidant status, catalase, native thiol, total thiol, albumin, and ceruloplasmin of the two groups did not show statistically significant difference (p > 0.05). Moreover, disulfide/total thiol and disulfide/native thiol ratios of the retinitis pigmentosa group were significantly greater in comparison to controls (p < 0.05). CONCLUSION: The researchers reached the conclusion that thiol oxidation in retinitis pigmentosa patients caused the dynamic thiol/disulfide homeostasis to shift toward the generation of disulfide. This is a novel research that involves analysis of thiol/disulfide homeostasis in retinitis pigmentosa patients using a novel automated assay. The researchers identified the cause for persistent oxidative stress and damage reported in retinitis pigmentosa patients. Still, future research is required for analysis of progression of antioxidant-oxidant state through various retinitis pigmentosa stages.

CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study.

PURPOSE: To investigate the natural history of RHO-associated retinitis pigmentosa (RP). METHODS: A multicenter, medical chart review of 100 patients with autosomal dominant RHO-associated RP. RESULTS: Based on visual fields, time-to-event analysis revealed median ages of 52 and 79 years to reach low vision (central visual field <20°) and blindness (central visual field <10°), respectively. For the best-corrected visual acuity (BCVA), the median age to reach mild impairment (20/67 ≤ BCVA < 20/40) was 72 years, whereas this could not be computed for lower acuities. Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%), in terms of decline rates of the BCVA (P < 0.001) and V4e retinal seeing areas (P < 0.005). The foveal thickness of the photoreceptor-retinal pigment epithelium (PR + RPE) complex correlated significantly with BCVA (Spearman's ρ = 0.733; P < 0.001). CONCLUSION: Based on central visual fields, the optimal window of intervention for RHO-associated RP is before the 5th decade of life. Significant differences in disease progression are present between generalized and sector RP phenotypes. Our findings suggest that the PR + RPE complex is a potential surrogate endpoint for the BCVA in future studies.

Changes of Serum Inflammatory Molecules and Their Relationships with Visual Function in Retinitis Pigmentosa.

Purpose: Retinal degeneration involves neuroinflammation, and pro-inflammatory cytokines/chemokines are markedly increased in the eyes of patients with retinitis pigmentosa (RP). In this study, we investigated the changes of serum cytokines/chemokines in RP, and their relationships with visual parameters. Methods: Forty-five consecutive patients with typical RP aged 20 to -39 years and 28 age-matched and gender-matched controls were included. Fifteen cytokines (interleukin [IL]-1α, IL-1ß, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p70, IL-13, 1L-15, IL-17, IL-23, interferon [IFN]-γ, and tumor necrosis factor [TNF]-α, TNF-ß) and 9 chemokines (eotaxin, growth-related oncogene [GRO]-α, I-309, IL-8, IFN-γ-inducible protein [IP]-10, monocyte chemotactic protein [MCP]-1, MCP-2, regulated activation normal T-cell expressed and secreted [RANTES], and thymus and activated regulated chemokine [TARC]) in the serum were simultaneously measured by a multiplexed immunoarray (Q-Plex). Relationships between these cytokines/chemokines and indices of central vision, such as visual acuity (VA), the values of static perimetry tests (Humphrey Field analyzer, the central 10-2 program), and optical coherence tomography measures were analyzed in the patients with RP. Results: Among the 15 cytokines and 9 chemokines, serum IL-8 and RANTES levels were significantly increased in patients with RP compared with controls (IL-8: P < 0.0001; RANTES: P < 0.0001). Among the elevated cytokines/chemokines, the levels of IL-8 were negatively correlated with VA (ρ = 0.3596 and P = 0.0165), and the average retinal sensitivity of four central points (ρ = -0.3691 and P = 0.0291), and 12 central points (ρ = -0.3491 and P = 0.0398), as well as the central subfield thickness (ρ = -0.3961 and P = 0.0094), and ellipsoid zone width (ρ = -0.3841 and P = 0.0120). Conclusions: Peripheral inflammatory response may be activated and serum IL-8 levels are associated with central vision in patients with RP.

Relationships Between Serum Antioxidant and Oxidant Statuses and Visual Function in Retinitis Pigmentosa.

Purpose: To investigate the serum changes of antioxidant/oxidant markers and the relationship between these factors and visual function in patients with retinitis pigmentosa (RP). Methods: Fifty-two RP patients <40 years old and 25 controls were included. Serum samples were analyzed for superoxide dismutase 3 (SOD3) activity, glutathione peroxidase (GPx), potential antioxidant (PAO), and hexanoyl-lysine (HEL). The relationships between these markers and visual parameters, including best-corrected visual acuity (BCVA), mean deviation (MD), and average retinal sensitivity of 4 or 12 central points on static perimetry tests (Humphrey Field Analyzer, the central 10-2 program) were examined in the RP patients. Results: Although there was no significant difference in the serum SOD3 activity between RP patients and controls, serum SOD3 activity in the severe degeneration group with macular involvement (16.3 ± 11.3 U/mL) was significantly lower compared with those in the mild degeneration group (those with midperipheral scotomas; 28.5 ± 16.6 U/mL, P = 0.0459). SOD3 was significantly related to visual acuity (r = -0.3701, P = 0.0069) and the average retinal sensitivity of four central points (r = 0.3463, P = 0.0137) in RP patients. The linear trends of these two parameters across SOD3 levels were also significant (P = 0.0264 and 0.0172, respectively). There was no consistent correlation between other serum antioxidant/oxidant markers and visual parameters. Conclusions: Lower serum SOD3 activity was associated with the severe retinal degeneration in RP patients. Our results suggest that serum SOD3 activity may be related to disease severity in RP.

Myoclonus epilepsy, retinitis pigmentosa, leukoencephalopathy and cerebral calcifications associated with a novel m.5513G>A mutation in the MT-TW gene.

We sequenced the mitochondrial genome from a 40-year-old woman with myoclonus epilepsy, retinitis pigmentosa, leukoencephalopathy and cerebral calcifications. Histological and biochemical features of mitochondrial respiratory chain dysfunction were present. Direct sequencing showed a novel heteroplasmic mutation at nucleotide 5513 in the MT-TW gene that encodes tRNATrp. Restriction Fragment Length Polymorphism analysis confirmed that about 80% of muscle mtDNA harboured the mutation while it was present in minor percentages in mtDNA from other tissues. The mutation is predicted to disrupt a highly conserved base pair within the aminoacyl acceptor stem of the tRNA. This is the 17° mutation in MT-TW gene and expands the known causes of late-onset mitochondrial diseases.

C-Reactive protein and progression of vision loss in retinitis pigmentosa.

PURPOSE: Chronic inflammation is involved in retinitis pigmentosa (RP). We demonstrated previously that intraocular inflammatory levels, as measured by slit-lamp ophthalmoscopy or laser flare photometry, are inversely correlated with central visual function in patients with RP. Here, we investigated the relationship between serum high-sensitivity C-reactive protein (hs-CRP) and visual parameters in RP. METHODS: We studied 58 consecutive typical patients with RP <40 years old and 29 age- and gender-matched controls. High-sensitivity C-reactive protein (hs-CRP) was detected by immunoturbidimetry. The relationships between hs-CRP and visual parameters including best-corrected visual acuity (BCVA), mean deviation (MD) of static perimetry tests (Humphrey Field Analyzer, the central 10-2 programme) and VA changes over the prior 5 years and MD changes over the prior 3 years were analysed in the patients with RP. RESULTS: The serum hs-CRP levels of the patients with RP were significantly higher than those of the controls (0.06 ± 0.08 versus 0.03 ± 0.04 mg/dl, p = 0.0119). In the patients with RP, there was no correlation of hs-CRP with cross-sectionally assessed VA or MD, but the baseline hs-CRP was significantly correlated with the MD deterioration (r = -0.4073, p = 0.0314). CONCLUSION: The average serum hs-CRP was significantly increased in the patients with RP, and higher hs-CRP was associated with faster deterioration of central visual function. These results suggest that the systemic inflammatory profile is altered and may be associated with disease progression in RP.

Vitamin A deficiency due to bi-allelic mutation of RBP4: There's more to it than meets the eye.

Vitamin A deficiency is the leading cause of preventable blindness in children worldwide and results in a well-recognized ocular phenotype. Herein we describe a patient presenting to the eye clinic with a retinal dystrophy and ocular colobomata. This combination of clinical signs and consanguineous pedigree structure suggested a genetic basis for the disease, a hypothesis that was tested using whole genome sequencing. Bi-allelic mutations in RBP4 were identified (c.248+1G>A), consistent with a diagnosis of inherited vitamin A deficiency. We describe a constellation of signs that appear to be characteristic for this disease, increasing clinical awareness of this rare condition.

Increased Plasma cGMP in a Family With Autosomal Recessive Retinitis Pigmentosa Due to Homozygous Mutations in the PDE6A Gene.

PURPOSE: To describe genotype and phenotype in a family with autosomal recessive retinitis pigmentosa (arRP) carrying homozygous mutations in the gene for the α-subunit of cyclic guanosine monophosphate (cGMP)-hydrolyzing phosphodiesterase 6 (PDE6A). Moreover, to compare their plasma cGMP levels to controls, exploring the possible role for cGMP in RP diagnostics. METHODS: Seven siblings and their parents were recruited. Microarray, verified by Sanger sequencing, was used for genotyping. Investigations included slit lamp and fundus examination, Goldmann perimetry, full-field and multifocal electroretinography (ERG), and optical coherence tomography (OCT). Cyclic GMP was measured with an immunoassay kit. RESULTS: All siblings and their father were homozygous, and the mother heterozygous, for IVS6+1G>A in PDE6A. Seven family members also carried c1532G>A in ABCA4. Visual fields were constricted with mere central remnants in older subjects and additional temporal crescents in younger subjects. Visual acuity ranged from 0.8 to amaurosis. Full-field ERGs showed extinguished rod responses and minimal cone responses. Multifocal ERGs were severely reduced. Optical coherence tomography revealed either general attenuation or central macular edema. Mean plasma cGMP in patients was approximately twice that in controls. CONCLUSIONS: To our knowledge, this is the first phenotypic description of arRP due to homozygous IVS6+1G>A mutations in PDE6A and these seem here to be associated with severe RP leading to early extinction of rod responses as well as reduced macular function. Additionally, patients showed increased plasma levels of cGMP, indicating a possible role for cGMP measurements as part of the clinical tests for this and, after further investigations, maybe other forms of RP.

Retinal oxygen saturation in retinitis pigmentosa and macular dystrophies in asian-Indian eyes.

PURPOSE: To study the oxygen-saturation profiles in RP and macular dystrophies and compare them with age-matched healthy controls. METHODS: In a cross-sectional prospective study, 62 subjects with RP, 23 with macular dystrophies, and 78 controls were enrolled, and retinal oximetry was performed with the Oxymap T1 retinal oximeter. The images were analyzed for oxygen saturation and diameter of retinal vessels. RESULTS: All parameters showed a significant difference among the three groups. Patients with RP showed significantly lower diameters (98.4 µm and 136.9 µm arteriolar and venous) (P < 0.001), higher saturations (102.3% and 59.1%) (P < 0.001; 0.06), and higher arterio-venous saturation difference (AVSD) (43%) (P < 0.001) compared with the other two groups. Macular dystrophies showed higher global arteriolar values (96.7%) and AVSD (41.6%) but comparable venous values (54.9%) to the control group (90.6%, 57.4%, and 33.3%). CONCLUSIONS: Oximetry is sensitive in quantifying hemodynamic changes in retinal dystrophies. It is still unclear whether these hemodynamic changes are a cause or a result of the disease process.

Endothelin-1 Plasma Levels in Patients with both Retinitis Pigmentosa and Flammer Syndrome.

BACKGROUND: Endothelin-1 is a strong endogenous vasoconstrictor and is also an agent reducing the ocular blood flow. Patients with retinitis pigmentosa are known to have reduced ocular blood flow. This can be secondary to retinal atrophy, but may also partially result from an additional condition, such as a Flammer syndrome. The aim of the study was to investigate whether the endothelin-1 plasma levels in retinitis pigmentosa patients with and without Flammer syndrome are different. PATIENTS AND METHODS: In the study we included patients with clinical signs and symptoms of retinitis pigmentosa, confirmed by electrophysiological findings. Blood samples were obtained from 6 retinitis pigmentosa patients with and 4 without Flammer syndrome. The results were related to 30 age- and sex-matched control subjects. Endothelin-1 plasma levels were determined by specific radioimmunoassay. RESULTS: The endothelin-1 plasma levels in retinitis pigmentosa patients with Flammer syndrome were significantly higher than those without Flammer syndrome. The mean (±SD) endothelin-1 levels (pg/mL) in retinitis pigmentosa patients with Flammer syndrome were 4.95 (±1.74), range: (2.37-6.76), whereas in patients without Flammer syndrome they were 1.10 (±0.08), range: 1.00-1.20. Our own normal values are: 1.56 (±0.30), range: (0.90-2.13). All retinitis pigmentosa patients with increased endothelin-1 plasma levels had signs and symptoms related to a Flammer syndrome, such as cold extremities, low blood pressure, reduced feeling of thirst, increased sensitivity in general, e.g., increased sensitivity to certain drugs, increased pain sensitivity and increased sense of smell. CONCLUSION: Endothelin-1 plasma levels were increased in retinitis pigmentosa patients with but not in patients without Flammer syndrome. Many questions remain open: Why so many retinitis pigmentosa patients suffer from Flammer syndrome, why is the endothelin-1 level in such patients higher than in healthy subjects with Flammer syndrome, how much of the ocular blood flow reduction is due to retinal degeneration and how much to the Flammer syndrome? We hypothesise that Flammer syndrome leads to an additional increase of the endothelin-1 level and an additional decrease of ocular blood flow in retinitis pigmentosa patients. Further studies are needed to analyse the causal relationship between retinitis pigmentosa and Flammer syndrome and evaluate potential therapeutic implications.

ET-1 plasma levels, choroidal thickness and multifocal electroretinogram in retinitis pigmentosa.

AIM: To assess the relationship between both photoreceptor function and choroidal thickness and endothelin-1 (ET-1) plasma levels in patients with early stage retinitis pigmentosa (RP). MAIN METHODS: We compared 24 RP patients (14 males and 10 females), 25 to 42 years of age (mean age: 34±7 years) with 24 healthy controls (12 males and 12 females) aged between 28 and 45 years (mean 36±6.8 years). All patients underwent visual field test, electroretinogram and multifocal-electroretinogram and choroidal thickness measurement by using spectral domain optical coherence tomography. KEY FINDINGS: RP patients had a visual acuity of 0.95, a mean defect of the visual field of -7.90±1.75 dB, a pattern standard deviation index of 6.09±4.22 dB and a b-wave ERG amplitude of 45.08±8.24 µV. Notably RP subjects showed significantly increased ET-1 plasma levels and reduced choroidal thickness compared with controls: respectively, 2.143±0.258 pg/ml vs. 1.219±0.236 pg/ml; p<0.002 and 226.75±76.37 µm vs. 303.9±39.87 µm; p<0.03. Spearman's correlation test highlighted that the increase of ET-1 plasma levels was related with the decrease of choroidal thickness (r=-0.702; p<0.023) and the increase of implicit time in both ring 2 (r=-0.669; p<0.034) and ring 3 (r=-0.883; p<0.007) of mfERG. SIGNIFICANCE: Increased ET-1 plasma levels may play a key role in the impairment of retinal and choroidal blood flow due to the vasoconstriction induced by ET-1. This could lead to worsening of the abiotrophic process of the macular photoreceptors.

Aberrant dolichol chain lengths as biomarkers for retinitis pigmentosa caused by impaired dolichol biosynthesis.

We observed a characteristic shortening of plasma and urinary dolichols in retinitis pigmentosa (RP) patients carrying K42E and T206A mutations in the dehydrodolichol diphosphate synthase (DHDDS) gene, using liquid chromatography-mass spectrometry. Dolichol-18 (D18) became the dominant dolichol species in patients instead of dolichol-19 (D19) in normal individuals. The D18/D19 ratio was calculated and used as an index of dolichol length distribution. K42E/K42E and K42E/T206A patients have significantly higher plasma and urinary D18/D19 ratios than K42E and T206A carriers. The ratios of carriers are significantly higher than normal individuals. Receiver operating characteristic (ROC) analysis shows that plasma and urinary D18/D19 ratios can unambiguously discriminate patients from carriers, and carriers from normal individuals. Dolichol analysis also provides evidence that the T206A mutation is RP-causative. The methodologies and procedures used for dolichol profiling are reliable, high throughput, and cost effective. Dolichol profiling, complementary to genotyping, can be readily adapted as a test in the clinic not only for the diagnosis of patients but also for identification of carriers with DHDDS or other genetic mutations that may impair dolichol biosynthesis.

Altered antioxidant-oxidant status in the aqueous humor and peripheral blood of patients with retinitis pigmentosa.

Retinitis Pigmentosa is a common form of hereditary retinal degeneration constituting the largest Mendelian genetic cause of blindness in the developed world. It has been widely suggested that oxidative stress possibly contributes to its pathogenesis. We measured the levels of total antioxidant capacity, free nitrotyrosine, thiobarbituric acid reactive substances (TBARS) formation, extracellular superoxide dismutase (SOD3) activity, protein, metabolites of the nitric oxide/cyclic GMP pathway, heme oxygenase-I and inducible nitric oxide synthase expression in aqueous humor or/and peripheral blood from fifty-six patients with retinitis pigmentosa and sixty subjects without systemic or ocular oxidative stress-related disease. Multivariate analysis of covariance revealed that retinitis pigmentosa alters ocular antioxidant defence machinery and the redox status in blood. Patients with retinitis pigmentosa present low total antioxidant capacity including reduced SOD3 activity and protein concentration in aqueous humor. Patients also show reduced SOD3 activity, increased TBARS formation and upregulation of the nitric oxide/cyclic GMP pathway in peripheral blood. Together these findings confirmed the hypothesis that patients with retinitis pigmentosa present reduced ocular antioxidant status. Moreover, these patients show changes in some oxidative-nitrosative markers in the peripheral blood. Further studies are needed to clarify the relationship between these peripheral markers and retinitis pigmentosa.

Specific combination of compound heterozygous mutations in 17ß-hydroxysteroid dehydrogenase type 4 (HSD17B4) defines a new subtype of D-bifunctional protein deficiency.

BACKGROUND: D-bifunctional protein (DBP) deficiency is typically apparent within the first month of life with most infants demonstrating hypotonia, psychomotor delay and seizures. Few children survive beyond two years of age. Among patients with prolonged survival all demonstrate severe gross motor delay, absent language development, and severe hearing and visual impairment. DBP contains three catalytically active domains; an N-terminal dehydrogenase, a central hydratase and a C-terminal sterol carrier protein-2-like domain. Three subtypes of the disease are identified based upon the domain affected; DBP type I results from a combined deficiency of dehydrogenase and hydratase activity; DBP type II from isolated hydratase deficiency and DBP type III from isolated dehydrogenase deficiency. Here we report two brothers (16½ and 14 years old) with DBP deficiency characterized by normal early childhood followed by sensorineural hearing loss, progressive cerebellar and sensory ataxia and subclinical retinitis pigmentosa. METHODS AND RESULTS: Biochemical analysis revealed normal levels of plasma VLCFA, phytanic acid and pristanic acid, and normal bile acids in urine; based on these results no diagnosis was made. Exome analysis was performed using the Agilent SureSelect 50Mb All Exon Kit and the Illumina HiSeq 2000 next-generation-sequencing (NGS) platform. Compound heterozygous mutations were identified by exome sequencing and confirmed by Sanger sequencing within the dehydrogenase domain (c.101C>T; p.Ala34Val) and hydratase domain (c.1547T>C; p.Ile516Thr) of the 17ß-hydroxysteroid dehydrogenase type 4 gene (HSD17B4). These mutations have been previously reported in patients with severe-forms of DBP deficiency, however each mutation was reported in combination with another mutation affecting the same domain. Subsequent studies in fibroblasts revealed normal VLCFA levels, normal C26:0 but reduced pristanic acid beta-oxidation activity. Both DBP hydratase and dehydrogenase activity were markedly decreased but detectable. CONCLUSIONS: We propose that the DBP phenotype seen in this family represents a distinct and novel subtype of DBP deficiency, which we have termed type IV based on the presence of a missense mutation in each of the domains of DBP resulting in markedly reduced but detectable hydratase and dehydrogenase activity of DBP. Given that the biochemical testing in plasma was normal in these patients, this is likely an underdiagnosed form of DBP deficiency.

Autosomal dominant occult macular dystrophy with an RP1L1 mutation (R45W).

PURPOSE: To characterize clinical features in occult macular dystrophy (OMD) patients with the RP1L1 gene mutation (p.R45W), one of two previously described mutations in Japanese OMD patients. METHODS: Mutational screening of the RP1L1 gene was performed via polymerase chain reaction and direct sequencing for seven unrelated probands (one autosomal dominant and six sporadic probands) with OMD. A comprehensive ophthalmic examination was performed, including Cirrus optical coherence tomography. Full-field electroretinography (ERG), multifocal ERG, and focal macular ERG were performed. RESULTS: The heterozygous mutation (p.R45W) was found in only one female proband with autosomal dominant OMD, whose mother was also diagnosed with OMD and carried the mutation. Ophthalmoscopy showed bilateral normal fundi in the proband but subtle retinal pigment epithelium mottling in the mother. Both the proband and her mother had typical OMD findings: decreased visual acuity and markedly reduced central responses in the multifocal ERG and focal macular ERG. Although full-field ERG revealed normal rod and standard combined responses, photopic and 30-Hz flicker responses were slightly reduced in both the proband and her mother. Optical coherence tomography revealed that the external limiting membrane and inner segment-outer segment boundary were disorganized despite normal macular thickness in the proband, whereas the mother exhibited macular thinning with discontinuous reflectivity of the external limiting membrane and inner segment-outer segment boundary. CONCLUSIONS: The clinical phenotypes differed between the proband and her mother and were indistinguishable from other sporadic or RP1L1-unassociated OMD patients, suggesting that mutation-dependent clinical features may not be present.

ET-1 plasma levels and ocular blood flow in retinitis pigmentosa.

Retinitis pigmentosa (RP) is an inherited retinal disorder clinically characterized by a pale, waxy optic nerve head, attenuated retinal blood vessels, and bone spicule pigment in the retina. Hemodynamic studies have demonstrated that RP is associated with a reduction in the retinal and choroidal blood flow. Retinal hemodynamic impairment is also present in early stages of RP, and various hypotheses have been advanced as to the cause. The authors studied 20 patients, 12 males and 8 females, aged 26-42 years (mean 35.1 years) and affected by simplex RP. The patients had a visual acuity of 0.9 +/- 0.1, visual field mean defect of -6.52 +/- 3.58 dB, and b-wave electroretinogram amplitude of 260.08 +/- 8.24 microV. An increase in plasma levels of endothelin-1 (ET-1) was found: 1.910 +/- 0.317 pg/mL versus 1.180 +/- 0.210 pg/mL in non-RP controls (p < 0.02). Moreover both an ocular and systemic vascular impairment was detected by means of color Doppler imaging and laser Doppler flowmetry performed during a cold pressor test. We found a correlation between the increase of ET-1 plasma levels in RP and the decrease of peak systolic velocity in the ophthalmic artery (p < 0.03) and in the posterior ciliary arteries (p < 0.006). It is thought that an increase of ET-1 and retinal oxygen levels in RP could lead to vasoconstriction and a decrease of the retinal blood flow, worsening the abiotrophic process.