Coats' disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: a role for norrin in retinal angiogenesis

CLINICAL CHARACTERISTICS AND TREATMENT OUTCOMES OF COATS DISEASE IN A SAUDI ARABIAN POPULATION

PURPOSE

To present the clinical aspects and treatment outcomes of Coats disease in Saudi Arabia.

METHODS

A retrospective chart review was performed of 92 patients (97 eyes) diagnosed with Coats disease at King Khalid Eye Specialist Hospital from 1983 to 2010.

RESULTS

The most common presenting complaint was decreased visual acuity followed by strabismus and then leukocoria. Snellen visual acuity was 20/20 to 20/50 in 9 eyes (9%), 20/50 to 20/160 in 11 eyes (11%), 20/200-counting fingers in 29 eyes (30%), and hand motion to no light perception in 24 eyes (25%). Telangiectasia was located in the preequatorial area in 71 eyes (73%) and most commonly involved the temporal retina in 67 eyes (69%). In eyes with clear view to the fundus, quadrant involvement by telangiectasia had the following distribution: 1) quadrant (n = 36, 37%); 2) quadrants (n = 26, 27%); 3) quadrants (n = 8, 8%); and 4 quadrants (n = 15, 15%). Total retinal detachment was present at presentation in 28 eyes (29%) and neovascular glaucoma in 8 (8%). Based on the Shields classification, the eyes were Stage 1 (n = 1, 1%), Stage 2A (n = 7, 7%), Stage 2B (n = 23, 24%), Stage 3A1 (n = 26, 27%), Stage 3A2 (n = 12, 12%), Stage 3B (n = 16, 17%), Stage 4 (n = 11, 11%), and Stage 5 (n = 5, 1%). Stage 3A was the most commonly presented stage (39%). Primary management included cryotherapy (19%), laser photocoagulation (64%), intravitreal agents (9%), and surgical drainage (4%). Combination treatment was performed in 29% of eyes. Thirteen eyes (13%) were enucleated because of clinical suspicion of retinoblastoma or the presence of glaucoma. Factors that were associated with a poor visual outcome of 20/200 or worse included age less than 10 years (relative risk: 1.27), Stages 3 and 4 disease (relative risk: 1.40), presence of subretinal fluid in all 4 quadrants including the fovea (relative risk: 14.25), and initial visual acuity of 20/200 (relative risk: 6.72) or worse (P < 0.005 for all factors).

CONCLUSION

Although rare, Coats disease is usually advanced at presentation and has a poor visual prognosis in the Saudi population, like in other populations. The findings of this study give validity and applicability to the Shields staging scheme, which we recommend using in clinical practice.

[Leber-Coats' disease: A retrospective study of 10 patients]

INTRODUCTION

Retrospective study analyzing clinical characteristics and treatment of children affected by Leber-Coats' disease.

METHOD

Children with Leber-Coats' disease seen in Edouard-Herriot Hospital, Lyon, between January 2004 and September 2013 were included. The following clinical characteristics were reported: sex, age at diagnosis, presenting symptom, Shields' stage, treatment used, and visual outcomes.

RESULTS

Ten children were included in our study. Mean age at diagnosis was 5.5 years. The disease was unilateral in 9/10 cases. The presenting symptom was loss of vision in 7/10 cases, strabismus in 3/10 cases, and microphthalmos in 1 case. The diagnosis was made fortuitously during a follow-up of familial congenital cataract in 2 patients. No cases of leukocoria were seen. Shields' stages were distributed as follows: stage 1, 2A and 2B: 1 case each, stage 3A1: 7 cases, stage>3A1: no cases. Laser photocoagulation was used up to stage 2B, combined with cryotherapy in stage 3A. Stage 1 and 2A were associated with relatively good final visual acuity. Significant macular lipid exudate (stage>2A) was associated with a worse prognosis.

CONCLUSION

These epidemiological data help us to better characterize these patients' prognosis. Early diagnosis seems to improve visual outcomes.

Haploinsufficiency of RCBTB1 is associated with Coats disease and familial exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) belongs to a group of genetically and clinically heterogeneous disorders in retinal vascular development. To date, in approximately 50% of patients with FEVR, pathogenic mutations have been detected in FZD4, LRP5, TSPAN12, NDP and ZNF408. In this study, we identified two heterozygous frameshift mutations in RCBTB1 from three Taiwanese cases through exome sequencing. In patient-derived lymphoblastoid cell lines (LCLs), the protein level of RCBTB1 is approximately half that of unaffected control LCLs, which is indicative of a haploinsufficiency mechanism. By employing transient transfection and reporter assays for the transcriptional activity of β-catenin, we demonstrated that RCBTB1 participates in the Norrin/FZD4 signaling pathway and that knockdown of RCBTB1 by shRNA significantly reduced nuclear accumulation of β-catenin under Norrin and Wnt3a treatments. Furthermore, transgenic fli1:EGFP zebrafish with rcbtb1 knockdown exhibited anomalies in intersegmental and intraocular vessels. These results strongly support that reduced RCBTB1 expression may lead to defects in angiogenesis through the Norrin-dependent Wnt pathway, and that RCBTB1 is a putative genetic cause of vitreoretinopathies.

A 6-year-old boy with Cornelia de Lange syndrome and Coats disease: case report and review of the literature

Cornelia de Lange syndrome (CdLS) can result in multiple congenital abnormalities and numerous ocular findings. We report the case of a 6-year-old boy with history of CdLS who presented with Coats disease. The findings in this case are compared to those found in the two previously reported cases of concomitant CdLS and Coats disease. The low incidence of these two disorders makes it highly unlikely that the connection is random in these 3 cases. The number of patients with both Cornelia de Lange syndrome and Coats disease is likely underestimated due to the difficulty in examining the peripheral retina in this patient population.

Bilateral Coats' Disease Combined with Retinopathy of Prematurity

Purpose. To report a case of bilateral Coats' disease combined with retinopathy of prematurity (ROP). Case. Retinal vascularization was complete in the right eye, whereas zone III, stage 3 ROP and preplus disease were observed in the left eye at 43 weeks of postmenstrual age (PMA) in a 31-week premature, 1200-g neonate. Intraretinal exudates developed and retinal hemorrhages increased in the left eye at 51 weeks of PMA. Diode laser photocoagulation (LP) was applied to the left eye. Exudates involved the macula, and telangiectatic changes developed one month following LP. Additional LP was applied to the left eye combined with intravitreal bevacizumab (IVB) injection at 55 weeks of PMA. Disease regressed one month after the additional therapy. At the 14-month examination of the baby, telangiectatic changes and intraretinal exudates were observed in the right eye. Diode LP was applied to the right eye combined with IVB injection. Exudates did not resolve completely, and cryotherapy was applied one month following LP. Retinal findings regressed three months following the cryotherapy. Conclusion. This is the first report of presumed bilateral Coats' disease combined with ROP. If Coats' disease could be diagnosed at early stages, it would be a disease associated with better prognosis.

Frizzled-4 Variations Associated with Retinopathy and Intrauterine Growth Retardation: A Potential Marker for Prematurity and Retinopathy

PURPOSE

To present the association between mutations affecting the Wnt-signaling receptor protein (FZD4), inherited vitreoretinopathies, and retinopathy of prematurity (ROP).

DESIGN

Retrospective analysis of prospective samples at a tertiary referral center.

PARTICIPANTS

Patients referred to our practice for management of a variety of pediatric vitreoretinopathies were offered participation in an ophthalmic biobank (421 participants with vitreoretinopathies were included in this study). Full-term healthy infants (n = 98) were recruited to the study as controls.

METHODS

Patients with various vitreoretinopathies were prospectively enrolled in an ophthalmic biobank, approved by the Human Investigation Committee at William Beaumont Hospital. Retrospective genetic analysis of the FZD4 gene was performed (Sanger sequencing). Participants with a diagnosis of familial exudative vitreoretinopathy (FEVR), Norrie disease, Coats' disease, bilateral persistent fetal vasculature, and ROP were reviewed for the presence of a FZD4 variant. Data retrieval included status of retinopathy (including staging when possible), gestational age (GA), birth weight (BW) (when available), and family and birth histories.

MAIN OUTCOME MEASURES

The association of FZD4 variants with the presence of vitreoretinopathy.

RESULTS

The sequence variation p.[P33S(;)P168S] is the most prevalent FZD4 variant and is statistically significant for ROP and FEVR (P = 4.6E-04 and P = 2.4E-03, respectively) compared with full-term newborns (P = 1.7E-01). In addition, infants expressing the sequence variation tended to have significantly lower BWs for respective GA (P = 0.04). This suggests that the FZD4 p.[P33S(;)P168S] variant may be a risk factor for retinopathy and restricted intrauterine growth.

CONCLUSIONS

Testing for FZD4 gene mutations is useful in patients with suspected FEVR and ROP. The relatively high prevalence of the p.[P33S(;)P168S] variant in ROP and intrauterine growth restriction suggests that it also may be a marker for increased risk of developing ROP and preterm birth.

Complex genetics of familial exudative vitreoretinopathy and related pediatric retinal detachments

Familial exudative vitreoretinopathy (FEVR) is a hereditary vitreoretinal disorder that can cause various types of retinal detachments. The abnormalities in eyes with FEVR are caused by poor vascularization in the peripheral retina. The genetics of FEVR is highly heterogeneous, and mutations in the genes for Wnt signaling and a transcription factor have been reported to be responsible for FEVR. These factors have been shown to be the regulators of the pathophysiological pathways of retinal vascular development. Studies conducted to identify the causative genes of FEVR have uncovered a diverse and complex relationship between FEVR and other diseases; for example, Norrie disease, a Mendelian-inherited disease; retinopathy of prematurity, a multifactorial genetic disease; and Coats disease, a nongenetic disease, associated with pediatric retinal detachments.

Familial exudative vitreoretinopathy and related retinopathies

Familial exudative vitreoretinopathy (FEVR) is a rare inherited disorder of retinal angiogenesis. Cases can be autosomal dominant, autosomal recessive, or X-linked. FEVR patients have an avascular peripheral retina which, depending on the degree of ischaemia, causes the secondary complications of the disease. Expressivity may be asymmetric and is highly variable. Five genes have been identified that when mutated, cause FEVR; NDP (X-linked), FZD4 (autosomal dominant and recessive), LRP5 (autosomal dominant and recessive), TSPAN12 (autosomal dominant and recessive), and ZNF408 (autosomal dominant). Four of these genes have been shown to have a central role in Norrin/Frizzled4 signalling, suggesting a critical role for this pathway in retinal angiogenesis. In addition to the ocular features, LRP5 mutations can cause osteopenia and osteoporosis. All FEVR patients in whom molecular testing is not easily accessible should have dual energy X-ray absorptiometry (DEXA) scans to assess bone mineral density, as treatment can be initiated to reduce the risk of bone fractures.

Coats' disease in Tanzania: first case report and literature review

BACKGROUND

Coats' disease is an exudative retinal detachment with vascular telangiectasis occurring mostly in male children, the age group most affected by retinoblastoma.

OBJECTIVES

Compare the differential diagnoses of Coats' disease Establish recommendation to early disease detection.

MATERIALS AND METHODS

A 3-year-old female child was referred to Muhimbili National Hospital (MNH), Tanzania, in September 2011. She had presented at the peripheral hospital with gradual onset of left eye leukocoria for 1 year and pain for 2 months. B-scan showed a mass in the left eye. A clinical diagnosis of retinoblastoma was made. Left eye enucleation was performed; the patient was referred to MNH, with the enucleated specimen.

RESULTS

Brain and orbits scan revealed no residual tumour. The globe measured 2 x 1.8 cm, the optic nerve stump measured 3 mm. A whitish mass filled the vitreous, with complete retinal detachment. Microscopy showed retinal gliosis, detachment with sub retinal PAS positive exudates, vacuolation and cholesterol clefts. Foreign body giant cells were present; telangiectatic thin-walled blood vessels were identified. Clinico-pathological findings were of stage 4 Coats' disease.

CONCLUSION

Coats' disease is an important differential diagnosis of retinoblastoma. Delay to detect Coats' disease leads to vision loss which necessitates eye enucleation as was in this child.

Retinoschisis in the setting of Coats' disease

This is a report of a 5-year-old boy who presented with an exudative retinopathy consistent with Coats' disease. Optical coherence tomography confirmed the concurrent presence of retinoschisis in the same eye, adjacent to the areas of exudation and ischemia. Treatment with laser photocoagulation, corticosteroids, and anti-VEGF therapy led to the resolution of the schisis cavity 1 year later. This represents the second published account of retinoschisis in the setting of Coats' disease.

Peripheral retinal nonperfusion in fellow eyes in coats disease

PURPOSE

To measure peripheral nonperfusion and describe bilateral vascular abnormalities in patients with Coats disease, emphasizing subtle findings in the contralateral eyes of patients diagnosed with unilateral disease.

METHODS

Clinical records, including retina drawings and fluorescein angiography images obtained under anesthesia, were retrospectively reviewed from consecutive pediatric patients with Coats disease. The main outcome measure was disk diameters of peripheral nonperfusion and proportion of Coats disease patients with bilateral findings.

RESULTS

Twenty-two of 32 patients with Coats disease had bilateral abnormal peripheral vasculature. In Group 1 (classic Coats disease: presumed unilateral, ocular only disease), 15 of 24 patients had peripheral nonperfusion >2 disk diameters in their contralateral eyes, 5 with telangiectasis and/or microaneurysms. Seven of 8 patients in Group 2 (Coats-like disease: systemic and/or clinically bilateral disease) had bilateral vascular anomalies.

CONCLUSION

Bilateral vascular abnormalities are more common in Coats disease than previously reported. This observation supports a systemic and/or genetic association with Coats disease. Patients with Coats disease should have careful evaluation of the periphery of the less affected eye, preferably with fluorescein angiography, to identify vascular changes not visible clinically. Both eyes warrant surveillance over the lifetime of the patient for potential progression to exudative disease that would warrant treatment.

A novel Norrie disease pseudoglioma gene mutation, c.-1_2delAAT, responsible for Norrie disease in a Chinese family

AIM

To investigate the genetic findings and phenotypic characteristics of a Chinese family with Norrie disease (ND).

METHODS

Molecular genetic analysis and clinical examinations were performed on a Chinese family with ND. Mutations in the Norrie disease pseudoglioma (NDP) gene were detected by direct sequencing. Haplotypes were constructed and compared with the phenotypes in the family. Evolutionary comparisons and mutant open reading frame (ORF) prediction were also undertaken.

RESULTS

Two family members with ocular manifestations were diagnosed with ND. No signs of sensorineural hearing loss were observed in either patient, while one of them showed signs of mild mental retardation. A novel heterozygous mutation in the NDP gene, c.-1_2delAAT, was detected in both patients. The mutation and the mutation bearing haplotype co-segregated with the ND phenotype in males and was transmitted from their mothers and/or grandmothers (II:2). The male without ND did not harbor the mutation. The mutation occurred at the highly conserved nucleotides. ORF finder predicted that the mutation would lead to the production of a truncated protein that lacks the first 11 N-terminal amino acids.

CONCLUSION

A novel mutation, c.-1_2delAAT in the NDP gene, was identified in a Chinese family with ND. This mutation caused ND without obvious sensorineural hearing loss. Mental disorder was found in one but not the other patients. The clinical heterogeneity in the family indicated that other genetic variants and epigenetic factors may also play a role in the disease presentation.

Cerebroretinal microangiopathy with calcifications and cysts associated with CTC1 and NDP mutations

Mutations in the conserved telomere maintenance component 1 (CTC1) gene were recently described in Coats plus syndrome and in cerebroretinal microangiopathy with calcifications and cysts. Norrie disease protein (NDP) gene was found mutated in Norrie disease, in Familial Exudative Vitreoretinopathy, and in Coats syndrome. Here we describe a boy affected by Norrie disease who developed typical features of cerebroretinal microangiopathy with calcifications and cysts. Direct sequencing of the CTC1 and NDP genes in this patient shows the presence of compound heterozygosity for 2 mutations in CTC1 (c.775G>A, pV259M and a novel microdeletion c.1213delG) and a missense mutation in the NDP gene (c.182T>C, p.L61P). Based on these genetic findings and on the expression of both genes in endothelial cells, we postulate that microangiopathy might be a primary underlying pathologic abnormality in cerebroretinal microangiopathy with calcifications and cysts. This hypothesis is further supported by magnetic resonance imaging (MRI) data showing multiple minute calcifications in the deep gray nuclei and in terminal arteriolar zones.

Current management of Coats disease

Since its original description in 1908, Coats disease has been recognized as an idiopathic cause of severe vision loss with a remarkable diversity in clinical presentation and morphology. Key clinical and imaging variables are helpful in differentiating Coats disease from life-threatening malignancies, and proper management revolves around a thorough knowledge of the differential diagnosis. Despite significant advancement in scientific understanding of the disease process and clinical spectrum, the underlying etiology remains obscure, and both primary and secondary forms are recognized. With the development of anti-VEGF therapy, vitreoretinal specialists have a new, effective adjunct to the clinical management of exudates, macular edema, and serous retinal detachment. We highlight the history, diagnostic challenges, evolving clinical spectrum, and current management of Coats disease.

Wnt/β-catenin signaling suppresses DUX4 expression and prevents apoptosis of FSHD muscle cells

Facioscapulohumeral muscular dystrophy is a dominantly inherited myopathy associated with chromatin relaxation of the D4Z4 macrosatellite array on chromosome 4. DUX4 is encoded within each unit of the D4Z4 array where it is normally transcriptionally silenced and packaged as constitutive heterochromatin. Truncation of the array to less than 11 D4Z4 units (FSHD1) or mutations in SMCHD1 (FSHD2) results in chromatin relaxation and a small percentage of cultured myoblasts from these individuals exhibit infrequent bursts of DUX4 expression. There are no cellular or animal models to determine the trigger of the DUX4 producing transcriptional bursts and there has been a failure to date to detect the protein in significant numbers of cells from FSHD-affected individuals. Here, we demonstrate for the first time that myotubes generated from FSHD patients express sufficient amounts of DUX4 to undergo DUX4-dependent apoptosis. We show that activation of the Wnt/β-catenin signaling pathway suppresses DUX4 transcription in FSHD1 and FSHD2 myotubes and can rescue DUX4-mediated myotube apoptosis. In addition, reduction of mRNA transcripts from Wnt pathway genes β-catenin, Wnt3A and Wnt9B results in DUX4 activation. We propose that Wnt/β-catenin signaling is important for transcriptional repression of DUX4 and identify a novel group of therapeutic targets for the treatment of FSHD.

Gene networks: dissecting pathways in retinal development and disease

During retinal neurogenesis, diverse cellular subtypes originate from multipotent neural progenitors in a spatiotemporal order leading to a highly specialized laminar structure combined with a distinct mosaic architecture. This is driven by the combinatorial action of transcription factors and signaling molecules which specify cell fate and differentiation. The emerging approach of gene network analysis has allowed a better understanding of the functional relationships between genes expressed in the developing retina. For instance, these gene networks have identified transcriptional hubs that have revealed potential targets and pathways for the development of therapeutic options for retinal diseases. Much of the current knowledge has been informed by targeted gene deletion experiments and gain-of-functional analysis. In this review we will provide an update on retinal development gene networks and address the wider implications for future disease therapeutics.

Primitive retinal vascular abnormalities: tumors and telangiectasias

Primitive retinal vascular abnormalities are benign conditions of the retinal circulation that comprise vascular tumors and telangiectasias. The principal vascular tumors of the retina include retinal capillary hemangioma, cavernous hemangioma of the retina, racemose hemangiomatosis of the retina and retinal vasoproliferative tumor, while primary retinal telangiectasias include Coats' disease, Leber's miliary aneurysms and idiopathic juxtafoveal telangiectasias. In most cases, these alterations result in significant visual impairment due to exudation determined by the structural abnormalities of the retinal vasculature. The aim of this review is to assess the different clinical and diagnostic features of the single pathological entities and to discuss the available treatment modalities including the onset of intravitreal antivascular endothelial growth factor therapy.

Fluorescein angiography to estimate normal peripheral retinal nonperfusion in children

PURPOSE

To estimate the normal distance from vascular termini to ora serrata in children's eyes.

METHODS

Clinical records and peripheral fluorescein angiography images of the ora serrata region, taken using scleral indentation and the RetCam system during examination under anesthesia, were retrospectively reviewed from consecutive patients with presumed normal peripheral retinal vasculature. All patients had ocular disease either only in the fellow eye or if in the study eye, to a degree judged not likely to affect peripheral retinal vascular development.

RESULTS

The record review identified 33 eyes of 31 patients with presumed normal peripheral vasculature. Mean age at angiography was 3.8 years (range, 2 months to 13 years). Mean area of nonperfusion was 0.9 disk diameters (DD) temporally (range, 1.5-0.5 DD; SD 0.3) and 0.6 DD nasally (range, 1-0.25 DD; SD 0.2).

CONCLUSIONS

In children up to 13 years of age, the avascular retina normally extends 1.5 DD or less temporally and 1.0 DD or less nasally from the ora serrata. Conservatively, ≥ 2 DD of nonperfusion, 3 standard deviations more than normal, should be considered abnormal and a sign of peripheral nonperfusion. These data may serve as preliminary indicators of the range of normal when evaluating diseases with retinal vascular abnormalities in children.

Screening for NDP mutations in 44 unrelated patients with familial exudative vitreoretinopathy or Norrie disease

PURPOSE

To screen mutations in the norrin (NDP) gene in 44 unrelated Chinese patients with familial exudative vitreoretinopathy (FEVR, 38 cases) or Norrie disease (6 cases) and to describe the associated phenotypes.

METHODS

Of the 44 patients, mutation in FZD4, LRP5, and TSPAN12 was excluded in 38 patients with FEVR in previous study. Sanger sequencing was used to analyze the 2 coding exons and their adjacent regions of NDP in the 44 patients. Clinical data were presented for patients with mutation.

RESULTS

NDP variants in 5 of the 6 patients with Norrie disease were identified, including a novel missense mutation (c.164G>A, p.Cys55Phe) in one patient, two known missense mutations (c.122G>A, p.Arg41Lys; c.220C>T, p.Arg74Cys) in two patients, and a gross deletion encompassing the two coding exons in two patients. Of the 5 patients, 3 had a family history and 2 were singleton cases. No mutation in NDP was detected in the 38 patients with FEVR.

CONCLUSIONS

NDP mutations are common cause of Norrie disease but might be rare cause for FEVR in Chinese.

Coats-like retinopathy in an infant with preclinical facioscapulohumeral dystrophy

Facioscapulohumeral dystrophy (FSHD) is an autosomal-dominant disorder characterized by weakness of the face, upper arm, shoulder, and lower limb musculature, with an onset between the first and third decades. Coats disease is a congenital disorder of retinal vascular development characterized by unilateral peripheral retinal telangiectasia and progressive subretinal and intraretinal exudation. This condition has a predilection for children and is usually isolated. Retinal vascular changes similar to those seen in Coats disease have been demonstrated by fluorescein angiography in 40% to 75% of patients with FSHD. Most patients have asymptomatic retinal telangiectasia found at ocular screening in adulthood after diagnosis of FSHD. We report a 7-month-old infant with bilateral Coats-like retinopathy in which the eye disease was discovered before findings of FSHD were clinically evident. To our knowledge, this patient represents the youngest reported case of preclinical FSHD with ocular disease.

Diagnosis and treatment of coats' disease: a review of the literature

Coats' disease is an idiopathic, ophthalmic condition characterized by retinal telangiectasis, intraretinal and subretinal exudation, which can lead to retinal detachment. It is mostly unilateral, progressive and affects mainly males during childhood, although adult cases have also been described. In this review, we make an update of the literature about Coats' disease, emphasizing on diagnosis and treatment, including the most recent treatment modalities, i.e. anti-vascular endothelial growth factor agents.

Norrin stimulates cell proliferation in the superficial retinal vascular plexus and is pivotal for the recruitment of mural cells

Mutations in Norrin, the ligand of a receptor complex consisting of FZD4, LRP5 and TSPAN12, cause severe developmental blood vessel defects in the retina and progressive loss of the vascular system in the inner ear, which lead to congenital blindness and progressive hearing loss, respectively. We now examined molecular pathways involved in developmental retinal angiogenesis in a mouse model for Norrie disease. Comparison of morphometric parameters of the superficial retinal vascular plexus (SRVP), including the number of filopodia, vascular density and number of branch points together with inhibition of Notch signaling by using DAPT, suggest no direct link between Norrin and Notch signaling during formation of the SRVP. We noticed extensive vessel crossing within the SRVP, which might be a loss of Wnt- and MAP kinase-characteristic feature. In addition, endomucin was identified as a marker for central filopodia, which were aligned in a thorn-like fashion at P9 in Norrin knockout (Ndp(y/-)) mice. We also observed elevated mural cell coverage in the SRVP of Ndp(y/-) mice and explain it by an altered expression of PDGFβ and its receptor (PDGFRβ). In vivo cell proliferation assays revealed a reduced proliferation rate of isolectin B4-positive cells in the SRVP from Ndp(y/-) mice at postnatal day 6 and a decreased mitogenic activity of mutant compared with the wild-type Norrin. Our results suggest that the delayed outgrowth of the SRVP and decreased angiogenic sprouting in Ndp(y/-) mice are direct effects of the reduced proliferation of endothelial cells from the SRVP.

Increased nitric oxide and vascular endothelial growth factor levels in the aqueous humor of patients with coats' disease

PURPOSE

To determine the aqueous humor levels of nitric oxide (NO) and vascular endothelial growth factor (VEGF) in the eyes of patients with Coats' disease and study the correlation between these levels.

METHODS

Samples of aqueous humor were obtained from 7 patients with Coats' disease and 15 age-matched patients with congenital cataracts as controls. Nitrite and nitrate (NOx), the stable end products of NO, were detected by the Griess reaction, and VEGF levels were assessed by enzyme-linked immunosorbent assay.

RESULTS

The aqueous humor NOx and VEGF levels were elevated in the eyes of patients with Coats' disease compared with those of controls (P=0.001 and P<0.001, respectively). The median NOx level was 55.2 μM (range, 23.0-75.3 μM) in the Coats' disease group and 18.8 μM (range, 8.7-36.2 μM) in the control group. The median VEGF level was 731.7 pg/mL (range, 288.3-1364.3 pg/mL) in the Coats' disease group and 33.3 pg/mL (range, 9.0-96.8 pg/mL) in the control group. No correlation was observed between the aqueous humor concentrations of NOx and VEGF.

CONCLUSIONS

NOx and VEGF are increased but not related in the aqueous humor samples of patients with Coats' disease. NO and VEGF may play roles in the pathogenesis of Coats' disease. Further studies are needed to clearly elucidate the relationship among VEGF, NO, and other cytokines in Coats' disease.

Unilateral sporadic retinal dysplasia: results of histopathologic, immunohistochemical, chromosomal, genetic, and VEGF-A analyses

PURPOSE

To describe new findings in a case of unilateral retinal dysplasia.

METHODS

Histopathologic evaluation of an enucleated globe and analysis with immunohistochemical probes, karyotyping, and genetic analysis for the Norrie gene, and aqueous assay for vascular endothelial growth factor A (VEGF-A).

RESULTS

Histopathological examination of the globe revealed retinal dysplasia with pseudorosette formation, abnormal or absent retinal nuclear lamination, a paucity of disorganized retinal microvasculature, retinal infoldings, advanced gliosis, persistent hyperplastic vitreous, exuberant neovascularization of the vitreous, and iris neovascularization (identical to the findings observed in bilateral Norrie disease). Immunohistochemistry disclosed GFAP-positive and GLUT-1-positive gliosis and retinal and persistent hyperplastic vitreous microvessels that were CD34-positive and GLUT-1-negative. Ki-67-positive retinal cells were polarized toward the subretinal space and absent in the retinal invaginations and pseudorosettes. A normal karyotype was found, and DNA sequencing revealed no known mutation in the region of the Norrie gene (NDP) in sputum or retinal DNA. Aqueous obtained immediately after enucleation contained an exceptionally high concentration of VEGF-A (4.5 ng/mL).

CONCLUSIONS

Despite the failure to find an abnormal NDP allele, other unexplored NDP regions, an undetected defect restricted to retinal tissues, or an autosomal mutation coupled with disrupted signaling pathways may be responsible for the condition. High aqueous VEGF-A suggests that this cytokine may play a role in pathogenesis in conjunction with other pathways.

Apelin is required for non-neovascular remodeling in the retina

Retinal pathologies are frequently accompanied by retinal vascular responses, including the formation of new vessels by angiogenesis (neovascularization). Pathological vascular changes may also include less well characterized traits of vascular remodeling that are non-neovascular, such as vessel pruning and the emergence of dilated and tortuous vessel phenotypes (telangiectasis). The molecular mechanisms underlying neovascular growth versus non-neovascular remodeling are poorly understood. We therefore undertook to identify novel regulators of non-neovascular remodeling in the retina by using the dystrophic Royal College of Surgeons (RCS) rat and the retinal dystrophy 1 (RD1) mouse, both of which display pronounced non-neovascular remodeling. Gene expression profiling of isolated retinal vessels from these mutant rodent models and wild-type controls revealed 60 differentially expressed genes. These included the genes for apelin (Apln) and for its receptor (Aplnr), both of which were strongly up-regulated in the mutants. Crossing RD1 mice into an Apln-null background substantially reduced vascular telangiectasia. In contrast, Apln gene deletion had no effect in two models of neovascular pathology [laser-induced choroidal neovascularization and the very low density lipoprotein receptor (Vldlr)-knockout mouse]. These findings suggest that in these models apelin has minimal effect on sprouting retinal angiogenesis, but contributes significantly to pathogenic non-neovascular remodeling.

Retinal vascular disease and the pathogenesis of facioscapulohumeral muscular dystrophy. A signalling message from Wnt?

The peripheral retinal vascular abnormality which accompanies FSHD belongs morphologically and clinically to a class of developmental 'retinal hypovasculopathies' caused by abnormalities of 'Wnt' signalling, which controls retinal angiogenesis. Wnt signalling is also fundamental to myogenesis. This paper integrates modern concepts of myogenic cell signalling and of transcription factor expression and control with data from the classic early ophthalmic and myology embryology literature. Together, they support an hypothesis that abnormalities of Wnt signalling, which activates myogenic programs and transcription factors in myoblasts and satellite cells, leads to defective muscle regeneration in FSHD. The selective vulnerability of different FSHD muscles (notably facial muscle, from the second branchial arch) might reflect patterns of transcription factor redundancies. This hypothesis has implications for FSHD research through study of transcription factors patterning in normal human muscles, and for autologous cell transplantation.

Coats' disease, Turner syndrome, and von Willebrand disease in a patient with Wildtype Norrie disease pseudoglioma

The authors describe a girl diagnosed as having Coats' disease, Turner syndrome (45X karyotype), and type 1 von Willebrand disease. She tested negative for the Norrie disease pseudoglioma (NDP) gene located on the X-chromosome, which has been suspected of contributing to Coats' disease.

The continuum of primary retinal telangiectasia

BACKGROUND

Primary retinal telangiectasia is characterized by abnormalities in the retinal vasculature. Any alteration of the normal retinal vasculature may result in variable degrees of retinal leakage, hemorrhages, and exudates. The retinal telangiectatic conditions of Coats' disease, Leber's miliary aneurysms, and idiopathic macular telangiectasia (IMT), although historically considered separate entities, may in fact be variants of the same pathophysiologic vascular process. This is based on observations noting that they share similarities in pathogenesis, histology, and clinical presentation. These observations are controversial and are contested in the literature. Conversely, others have documented Coats' disease, Leber's miliary aneurysms, and IMT as unique and separate retinal conditions, each with specific features.

METHODS

Three cases are presented spanning the spectrum of primary retinal telangiectasia. Clinical evaluation, dilated fundus examination, and auxiliary testing document both the similar characteristics that the entities share as well as the distinct features, which define each disease's nomenclature and categorization.

CONCLUSION

Coats' disease, Leber's miliary aneurysms, and IMT may be part of a singular clinical spectrum sharing pathophysiologic and histopathologic features and similarities in clinical presentation.

[Retinal involvement and genetic myopathy]

INTRODUCTION

In genetic diseases, association between retinal and muscular involvement is uncommon, quite specific and frequently allows the diagnosis. In this context, three types of retinal involvement have been described: retinitis pigmentosa (RP), pattern retinal dystrophy (PRD) and exudative retinitis resembling Coats disease (CD).

STATE OF THE ART

The association between RP, PRD and muscle weakness is highly evocative of a mitochondrial disorder. Extra ocular muscles may be affected, but limb girdle or distal weakness can also be present in association or not with symptoms and signs of multisystemic involvement. In a large number of patients suffering from facioscapulohumeral muscular dystrophy (FSHD), retinal vessels telangectasia can be found at the fundoscopic examination. This finding, which corresponds to a developmental abnormality of peripheral retinal blood vessels, is not progressive and remains clinically asymptomatic. Nevertheless, a few patients with FSHD can develop an exsudative retinopathy resembling Coats disease with the risk of the major complication, recurrent retinal detachments.

PERSPECTIVES AND CONCLUSIONS

Considering the diagnostic interest and the deleterious consequences that may follow retinal involvement, close collaboration between the neurologist and ophthalmologist is needed in order to establish the diagnosis, detect complications early, and set up appropriate therapies.

[Coats disease]

Coats disease is characterized by idiopathic congenital retinal telangiectasis and exudative retinopathy. Mostly young males are affected. The disease is usually unilateral. Visual prognosis varies from full visual acuity to blindness according to the extent of retinal exudation. Retinoblastoma is a major differential diagnosis particularly in small children but other causes of exudative retinopathy must also be considered. Treatment aims include obliteration of the telangiectasis in order to resolve retinal exudation and achieve reattachment of the retina. Therapeutic options comprise laser coagulation or cryotherapy, drainage of subretinal fluid, buckling surgery and pars plana vitrectomy. In more advanced cases with therapy-resistant secondary glaucoma enucleation may be required. More recently, intravitreal administration of VEGF inhibitors has become an option.

A population-based study of Coats disease in the United Kingdom I: epidemiology and clinical features at diagnosis

AIMS

coats disease is an uncommon form of retinal telangiectasis. Published case series mostly originate from tertiary referrals centres and may provide a skewed view of disease severity. We conducted a prospective population-based study of Coats disease in the United Kingdom to ascertain the incidence and provide a more representative picture.

METHODS

the study was conducted through the British Ophthalmological Surveillance Unit. This first paper reports the features at presentation; gender, mode of presentation, visual acuity, anterior and posterior segment findings, amount of retinal exudation, and disease staging.

RESULTS

a total of 55 eligible cases of Coats disease were identified giving an estimated population incidence of 0.09 per 100.000 of the population. All cases were unilateral and 85% were male. Mean age at presentation was 146 months (median 96 months). The mean age of diagnosis was markedly different with differing mechanisms of presentation. Cases presenting with leucocoria or strabismus presented early whereas subjective visual loss presented much later. A large proportion of eyes (44%) were blind at diagnosis. The great majority of eyes (71%) had 6 or fewer clock hours of retinal exudation. More severe forms/stages of Coats disease were more common in the youngest patients.

CONCLUSIONS

compared with published studies of Coats disease, we have found milder disease severity at presentation. This is most likely because of the population-based nature of our study reflecting the full disease spectrum. A large proportion of eyes with Coats have poor visual acuity and disease severity is worse in younger patients.

The effect of intravitreal bevacizumab in the treatment of Coats disease in children

PURPOSE

The purpose of this study was to determine if intravitreal bevacizumab can reduce subretinal exudates and exudative retinal detachment and facilitate the treatment of Coats disease in children.

METHODS

Prospective, interventional, and noncomparative case series of three eyes in three children with Coats disease were studied. All eyes received only intravitreal bevacizumab injection as the primary treatment. Ablative procedures, including cryotherapy, traditional continuous wave laser, or subthreshold diode micropulse laser, for diseased vessels were performed after subretinal fluid totally reabsorbed. One supplementary intravitreal bevacizumab injection was given after ablative procedures on the same day. The changes in pre- and postoperative best-corrected visual acuity were recorded. Serial color fundus photography, optical coherence tomography, and B-scan sonography were performed to measure treatment efficacy.

RESULTS

After receiving one to three injections, all three patients had subretinal fluid completely reabsorbed. All patients had one session of subsequent ablative procedures for diseased vessels and supplementary intravitreal bevacizumab injection. No patients had recurrent subretinal fluid. Improved visual acuity was noted in two cases but was not detectable in the other. No ocular or systemic complications related to bevacizumab were noted during the entire course of follow-up.

CONCLUSION

Intravitreal bevacizumab appears to be a well-tolerated treatment for children with Coats disease. A favorable response is observed when compared with other treatment modalities. It has the potential as an adjuvant therapy of vascular ablative procedures to improve final vision and facilitate ongoing treatment.

Coats' disease: an Indian perspective

Aim:

To describe the clinical features, treatment and outcome patterns in 307 eyes with Coats' disease.

Materials and Methods:

Retrospective chart review of patients diagnosed with Coats' disease between January 1996 and January 2006 from a single referral center in southern India.

Results:

Two hundred and eighty patients (307 eyes) with mean age of 15.67 years (range: Four months-80 years) were included. Decreased vision (77%), unilateral affection (90%) and male preponderance (83.4%) were chief presenting features. Anterior segment involvement was seen in 67 (21.8%) eyes. Retinal telangiectasia were seen in 302 (99%) eyes, exudation in 274 (89%) eyes and retinal detachment in 158 (51.5%) eyes. Four-quadrant disease was seen in 207 (67.2 %) eyes. Visual acuity was < 20/200 in 249 (80.9%) eyes. One hundred and nine of 176 treated eyes (61.93%) had favorable anatomical outcome; 207 of 280 eyes (74%) had an optimal structural outcome. Seventeen (5.3%) eyes were enucleated. Complications following treatment included phthisis bulbi (7%), neovascular glaucoma (5%), epiretinal membrane (4.4%) and rubeosis iridis (4.4%).

Conclusion:

Indian patients with Coats' disease have a high male predominance, the majority of whom present with severe visual impairment and extensive four-quadrant exudation. Unusual presentations such as pain, vitreous hemorrhage and a high incidence of anterior segment involvement are distinctive to Indian eyes.

Elevated vascular endothelial growth factor level in Coats' disease and possible therapeutic role of bevacizumab

PURPOSE

To compare intraocular vascular endothelial growth factor (VEGF) level in patients with and without Coats' disease, and to report a case of Coats' disease that responded to intravitreal injection of bevacizumab.

METHODS

Intraocular fluid was obtained from four eyes with Coats' disease (subretinal fluid in three eyes and aqueous in one eye) and from five eyes with rhegmatogenous retinal detachment (subretinal fluid in four eyes and vitreous in one eye). Intraocular VEGF level was compared between these two groups. In one eye with stage 2B Coats' disease, macular edema, visual acuity, and intraocular VEGF level were compared before and after intravitreal injection of bevacizumab.

RESULTS

Mean intraocular VEGF level in eyes with Coats' disease was 2,394.5 pg/ml, compared to 15.3 pg/ml in eyes with rhegmagenous retinal detachment. In the eye with stage 2B Coats' disease, macular edema was reduced after bevacizumab injection, and the visual acuity improved from 0.05 to 0.2. Intraocular VEGF level decreased from 1247 pg/ml to 20.4 pg/ml 1 month after the injection.

CONCLUSION

Coats' disease is associated with increased intraocular VEGF level. Bevacizumab may be a valuable adjunctive treatment for Coats' disease.

Novel and recurrent NDP gene mutations in familial cases of Norrie disease and X-linked exudative vitreoretinopathy

PURPOSE

To present the results of molecular analysis of the NDP gene in Mexican families with Norrie disease (ND) and X-linked familial exudative vitreoretinopathy (XL-FEVR).

METHODS

Two unrelated families with ND and two with XL-FEVR were studied. Clinical diagnosis was suspected on the basis of a complete ophthalmologic examination. Molecular methods included DNA isolation from peripheral blood leucocytes, polymerase chain reaction amplification and direct nucleotide sequencing analysis of the complete coding region and exon-intron junctions of NDP. Haplotype analysis using NDP-linked microsatellites markers was performed in both ND families.

RESULTS

A novel Norrin missense mutation, p.Arg41Thr, was identified in two apparently unrelated families with ND. Haplotype analysis demonstrated that affected males in these two families shared the same ND-linked haplotype, suggesting a common origin for this novel mutation. The previously reported p.Arg121Trp and p.Arg121Gln Norrin mutations were identified in the two families with XL-FEVR.

CONCLUSION

Our results expand the mutational spectrum in ND. This is the first report of ND resulting from mutation at arginine position 41 of Norrin. Interestingly, mutations at the same residue but resulting in a different missense change were previously described in subjects with XL-FEVR (p.Arg41Lys) or persistent fetal vasculature syndrome (p.Arg41Ser), indicating that the novel p.Arg41Thr change causes a more severe retinal phenotype. Preliminary data suggest a founder effect for the ND p.Arg41Thr mutation in these two Mexican families.

Coats-Type Retinal Telangiectasia in Case of Kabuki Make-Up Syndrome (Niikawa-Kuroki Syndrome)

PURPOSE

To report a case of Kabuki make-up syndrome (KMS) or Niikawa-Kuroki syndrome with Coats-type retinal telangiectasia, which has not been previously reported.

METHODS

Observational case report.

CONCLUSIONS

There have been only two reports of retinal pigmentation abnormalities and a single case of bilateral macular deposits in KMS, but this is the first report of a Coats type retinal telangiectasia. This case highlights the importance of thorough posterior segment examination in cases of KMS.

SNPs: impact on gene function and phenotype

Single nucleotide polymorphism (SNP) is the simplest form of DNA variation among individuals. These simple changes can be of transition or transversion type and they occur throughout the genome at a frequency of about one in 1,000 bp. They may be responsible for the diversity among individuals, genome evolution, the most common familial traits such as curly hair, interindividual differences in drug response, and complex and common diseases such as diabetes, obesity, hypertension, and psychiatric disorders. SNPs may change the encoded amino acids (nonsynonymous) or can be silent (synonymous) or simply occur in the noncoding regions. They may influence promoter activity (gene expression), messenger RNA (mRNA) conformation (stability), and subcellular localization of mRNAs and/or proteins and hence may produce disease. Therefore, identification of numerous variations in genes and analysis of their effects may lead to a better understanding of their impact on gene function and health of an individual. This improved knowledge may provide a starting point for the development of new, useful SNP markers for medical testing and a safer individualized medication to treat the most common devastating disorders. This will revolutionize the medical field in the future. To illustrate the effect of SNPs on gene function and phenotype, this minireview focuses on evidences revealing the impact of SNPs on the development and progression of three human eye disorders (Norrie disease, familial exudative vitreoretinopathy, and retinopathy of prematurity) that have overlapping clinical manifestations.

Vascular changes in the cerebellum of Norrin /Ndph knockout mice correlate with high expression of Norrin and Frizzled-4

X-linked Norrie disease, familial exudative vitreoretinopathy (FEVR), Coat's disease and retinopathy of prematurity are severe human eye diseases and can all be caused by mutations in the Norrie disease pseudoglioma gene. They all show vascular defects and characteristic features of retinal hypoxia. Only Norrie disease displays additional neurological symptoms, which are sensorineural hearing loss and mental retardation. In the present study, we analysed transcript levels of the ligand Norrin (Ndph) and its two receptors Frizzled-4 (Fzd4) and LDL-related protein receptor 5 (Lrp5) in six different brain regions (cerebellum, cortex, hippocampus, olfactory bulb, pituitary and brain stem) of 6- to 8-month-old wild-type and Ndph knockout mice by quantitative real-time PCR. No effect of the Ndph knockout allele on Fzd4 or Lrp5 receptor expression was found. Furthermore, no alterations of the transcript levels of three hypoxia-regulated angiogenic factors (Vegfa, Itgrb3 and Tie1) were observed in the absence of Norrin. Interestingly, we identified significant differences in Ndph, Fzd4 and Lrp5 transcript levels in brain regions of wild-type mice and observed highest expression of Norrin and frizzled-4 in cerebellum. Transcript analyses were correlated with morphological data obtained from cerebellum and immunohistochemical studies of blood vessels in different brain regions. Vessel density was reduced in the cerebellum of Ndph knockout mice but the number of Purkinje and granular cells was not altered. This provides the first description of a brain phenotype in Ndph knockout mice, which will help to elucidate the role of Norrin in the brain.