Electrophysiology of type II mesangiocapillary glomerulonephritis with associated fundus abnormalities

Retinal drusen are more common and larger in SLE with renal impairment

Introduction

Complement has been implicated in systemic lupus erythematosus (SLE) pathogenesis on the basis of the associations with inherited complement defects and genome-wide association study risk alleles, glomerular deposits, reduced serum levels, and occasional reports of retinal drusen. This study examined drusen in SLE and their clinical significance.

Methods

This cross-sectional observational study compared individuals with SLE recruited from renal and rheumatology clinics with hospital controls. Participants were reviewed for clinical features and underwent imaging with a nonmydriatic retinal camera. Deidentified images were examined by 2 trained graders for drusen number and size using a grid overlay.

Results

The cohort with SLE (n = 65) comprised 55 women (85%) and 10 men (15%) with a median age of 47 years (interquartile range 35–59), where 23 (35%) were of southern European or Asian ancestry, and 32 (49%) had biopsy-proven lupus nephritis. Individuals with SLE had higher mean drusen numbers than controls (27 ± 60, 3 ± 9, respectively, P = 0.001), more drusen counts ≥10 (31, 48% and 3, 5%, respectively, P < 0.001), and more medium-large drusen (14, 22% and 3, 5%, respectively, P < 0.001). In SLE, mean drusen counts were higher, and drusen were larger, with an estimated glomerular filtration rate (eGFR) <90 ml/min per 1.73 m² (P = 0.02, P = 0.02, respectively) or class IV nephritis (P = 0.03, P = 0.02).

Conclusion

Drusen composition resembles that of glomerular immune deposits. CFH controls complement activation in the extracellular matrix and CFH risk variants are shared by drusen in macular degeneration and by SLE. CFH represents a possible treatment target for SLE especially with renal impairment.

Bilateral macular drusen in acquired partial lipodystrophy with type 2 membranoproliferative glomerulonephritis

A 35-year-old woman with acquired partial lipodystrophy (PLD) and features of type 2 membranoproliferative glomerulonephritis (MPGN-II), presented with difficulty in her fine detailed vision over the past year. She had right amblyopia from a hypermetropic anisometropia with astigmatism, displaying a best-corrected visual acuity of 0.50 and 0.00 LogMAR, in the right and left eye, respectively. Funduscopy showed bilateral symmetrical drusenoid deposits most prominent in the temporal macula with clusters in the superior and inferior retina, outside the temporal vascular arcades. Multimodal retinal imaging was performed, which confirmed hyperautofluorescent drusen located between the retinal pigment epithelium and Bruch's membrane. Electroretinography showed bilateral mild peripheral macular dysfunction, but normal central macular function on the pattern electroretinogram. Both PLD and macular drusen, are rare as distinct disease entities, but an association does exist and may be linked to MPGN-II.

Revisiting the role of factor H in age-related macular degeneration: Insights from complement-mediated renal disease and rare genetic variants

Ophthalmologists are long familiar with the eye showing signs of systemic disease, but the association between age-related macular degeneration and abnormal complement activation, common to several renal disorders, has only recently been elucidated. Although complement activation products were identified in drusen almost three decades ago, it was not until the early 21st century that a single-nucleotide polymorphism in the complement factor H gene was identified as a major heritable determinant of age-related macular degeneration, galvanizing global efforts to unravel the pathogenesis of this common disease. Advances in proteomic analyses and familial aggregation studies have revealed distinctive clinical phenotypes segregated by the functional effects of common and rare genetic variants on the mature protein and its splice variant, factor H-like protein 1. The predominance of loss-of-function, N-terminal mutations implicate age-related macular degeneration as a disease of general complement dysregulation, offering several therapeutic avenues for its modulation. Here, we explore the molecular impact of these mutations/polymorphisms on the ability of variant factor H/factor H-like protein 1 to localize to polyanions, pentraxins, proinflammatory triggers, and cell surfaces across ocular and renal tissues and exert its multimodal regulatory functions and their clinical implications. Finally, we critically evaluate key therapeutic and diagnostic efforts in this rapidly evolving field.

Multimodal imaging of retinal pigment epithelial detachments in patients with C3 glomerulopathy: case report and review of the literature

Background

To describe the optical coherence tomography angiograhy (OCTA) of drusenoid pigment epithelial detachments (PEDs) in a woman affected by Complement 3 (C3) glomerulopathy, which represents a spectrum of glomerular diseases characterized on fluorescent microscopy by C3 accumulation with absent, or scanty, immunoglobulin deposits. It is due to acquired or genetically defective alternative pathway control and is generally associated with drusen-like deposits in Bruch’s membrane, as well as choriocapillaris. These retinal lesions can be associated with choroidal neovascularization and central serous chorioretinopathy (CSCR). OCTA is useful to detect neovascularization without injecting a contrast product, particularly in these patients who may have renal insufficiency.

Case presentation

A 28-year-old woman affected by C3 glomerulpathy was diagnosed with asymptomatic multiple bilateral PEDs during a routine ophthalmologic consultation. To better characterize the lesions, multimodal imaging was performed and included: optic coherence tomography (OCT), en-face OCT, OCTA, fluorescence and indocyanine angiography. The OCTA clearly identified vascular network rarefaction with decreased choriocapillary vascularization. It confirmed that PEDs associated with C3 glomerulonephritis are not vascularized, but rather of serous type.

Conclusions

Patients affected by C3 glomerulopathy can develop neovascular membranes as retinal complications of pigment epithelial detachments. Optical coherence angiography may be indicated to identify this complication, without injecting any contrast product that could produce further kidney damage.

A meta-analysis of clinical electro-oculography values

BACKGROUND

The aim of the meta-analysis was to derive a range of mean normal clinical electrooculogram (EOG) values from a systematic review of published EOG studies that followed the guidelines of the ISCEV standard for clinical electro-oculography.

METHODS

A systematic literature review was performed using four relevant databases limited to peer-reviewed articles in English between 1967 and February 2017. Studies reporting clinical EOG or FO normal values were included when the report used a standard 30° horizontal saccade, a retinal luminance of between 100 and 250 cd m^-2, and had > 10 subjects in their normative values. The search identified 1145 articles after duplicates were removed with subsequent screening of the abstracts excluding a further 1098, resulting in 47 full-text articles that were then assessed by the author (PC) with a final nine articles meeting the inclusion criteria. An overall effect estimate using inverse variance-weighted meta-analysis was performed to estimate the mean values for the light peak/dark trough ratio (LP:DT ratio) (dilated and undilated), the time to the LP, the amplitude of the LP, dark trough (DT) and the fast oscillation (FO) peak-to-trough ratio from the included studies.

RESULTS

The mean dilated LP:DT ratio was 2.35 (95% CI 2.28-2.42); undilated LP:DT ratio was 2.37 (95% CI 2.28-2.45); LP amplitude was 835 (95% CI 631-1039) µV and the mean time to the LP being 8.2 (95% CI 7.7-8.7) min. The mean DT amplitude was 358 (95% CI 292-424) µV, and the mean FO peak-to-trough ratio was 1.13 (95% CI 1.11-1.16). The results of the LP/DT ratio are drawn from studies with a mean ± standard deviation (SD) age of 34.08 ± 12.93 years for dilated and 33.65 ± 12.28 years for undilated LP/DT ratios.

CONCLUSIONS

The meta-analysis of EOG studies has generated a reference range of normal mean values for clinicians to refer to when using the ISCEV clinical EOG. It provides a potential method to generate similar data sets from published normal values in related visual electrophysiology tests.

Complement factor H in AMD: Bridging genetic associations and pathobiology

Age-Related Macular Degeneration (AMD) is a complex multifactorial disease characterized in its early stages by lipoprotein accumulations in Bruch's Membrane (BrM), seen on fundoscopic exam as drusen, and in its late forms by neovascularization ("wet") or geographic atrophy of the Retinal Pigmented Epithelial (RPE) cell layer ("dry"). Genetic studies have strongly supported a relationship between the alternative complement cascade, in particular the common H402 variant in Complement Factor H (CFH) and development of AMD. However, the functional significance of the CFH Y402H polymorphism remains elusive. In this article, we critically review the literature surrounding the functional significance of this polymorphism. Furthermore, based on our group's studies we propose a model in which CFH H402 affects CFH binding to heparan sulfate proteoglycans leading to accelerated lipoprotein accumulation in BrM and drusen progression. We also review the literature on the role of other complement components in AMD pathobiologies, including C3a, C5a and the membrane attack complex (MAC), and on transgenic mouse models developed to interrogate in vivo the effects of the CFH Y402H polymorphism.

Choroidal neovascularization in acquired partial lipodystrophy

PURPOSE

To report a case of choroidal neovascularization (CNV) associated with acquired partial lipodystrophy (PLD).


METHODS

A 55-year-old woman with a known history of PLD presented with acute onset visual loss affecting her right eye and underwent investigations to diagnose the underlying pathology.


RESULTS

Fluorescein angiography and time-domain optical coherence tomography demonstrated the presence of intraretinal edema consistent with CNV. The patient was treated with intravitreal ranibizumab with excellent results, and her vision remains unimpaired 4 years posttreatment.


CONCLUSIONS

Choroidal neovascularization is an angiogenic process that can occur following retinal pigment epithelium disruption of any cause. These vessels may then bleed into retinal tissue, with potentially devastating visual consequences. Although rare, PLD has been associated with retinal drusenoid lesions. This is the first case to report CNV in association with PLD, and highlights the importance of considering CNV in the differential diagnosis of acute visual loss in patients with drusenoid diseases such as PLD.

Regulated secretion of complement factor H by RPE and its role in RPE migration

BACKGROUND

Variants in the gene for complement factor H (CFH) have been implicated as a major risk factor for the development of age-related macular degeneration (AMD). Little is known, however, about the factors regulating local expression and secretion of CFH by retinal pigment epithelial cells (RPE).

METHODS

Cultured human early passage RPE cells, highly differentiated, polarized human RPE cultures, and bovine RPE explants were incubated in the presence or absence of recombinant human or bovine interferon-gamma (IFN-gamma; 25 ng/ml). CFH expression in cell lysates, and secretion into culture supernatants were examined by Western blot. CHF expression and localization was analyzed by confocal microscopy. Migration assay was performed in a modified Boyden chamber with early passage human RPE cells after stimulation with recombinant CFH protein (1-100 ng/ml).

RESULTS

CFH was expressed in the cell lysates of RPE cells, and this expression was significantly upregulated by IFN-gamma. Immunoreactivity for CFH was detected in RPE cells of bovine explants and highly differentiated human RPE monolayers, and the level of immunoreactivity increased after IFN-gamma stimulation. Confocal microscopy revealed that CFH was predominantly localized in the apical cytoplasm of polarized human RPE. Western blot confirmed that IFN-gamma increased CFH secretion into RPE supernatants. Dose-dependent RPE cell chemotactic migration was induced by CFH.

CONCLUSION

IFN-gamma promotes CFH expression in the apical compartment of RPE cells and increases secretion of CFH into RPE culture supernatants. Furthermore, CFH promotes chemotactic migration of RPE. This study suggests that interactions between CFH and IFN-gamma have the potential to play a role in the pathogenesis of AMD.

Microperimetric evaluation of macula in retinopathy of membranoproliferative glomerulonephritis type II: a case report

PURPOSE

To report on the microperimetric evaluation of the central visual field in a patient with retinopathy due to membranoproliferative glomerulonephritis.

METHODS

The central 20 degrees visual field was evaluated using fundus-related perimetry with (Nidek MP1) microperimeter in a patient with proven membranoproliferative glomerulonephritis type II, who had multiple drusen-like lesions involving the posterior pole of both eyes, with corresponding window defects on fundus fluorescein angiogram.

RESULTS

Static threshold perimetry of the central 20 degrees using a 10 dB threshold, Goldmann size II stimulus, with (Nidek-MP1) microperimeter showed reduction in retinal sensitivity in the parafoveal and in the temporal paramacular areas in both the eyes that had drusen-like lesions.

CONCLUSIONS

Early loss of function in retinopathy of membranoproliferative glomerulonephritis type II can probably be detected by fundus-related microperimetry.

A common haplotype in the complement regulatory gene factor H (HF1/CFH) predisposes individuals to age-related macular degeneration

Age-related macular degeneration (AMD) is the most frequent cause of irreversible blindness in the elderly in developed countries. Our previous studies implicated activation of complement in the formation of drusen, the hallmark lesion of AMD. Here, we show that factor H (HF1), the major inhibitor of the alternative complement pathway, accumulates within drusen and is synthesized by the retinal pigmented epithelium. Because previous linkage analyses identified chromosome 1q25-32, which harbors the factor H gene (HF1/CFH), as an AMD susceptibility locus, we analyzed HF1 for genetic variation in two independent cohorts comprised of approximately 900 AMD cases and 400 matched controls. We found association of eight common HF1 SNPs with AMD; two common missense variants exhibit highly significant associations (I62V, chi2 = 26.1 and P = 3.2 x 10(-7) and Y402H, chi2 = 54.4 and P = 1.6 x 10(-13)). Haplotype analysis reveals that multiple HF1 variants confer elevated or reduced risk of AMD. One common at-risk haplotype is present at a frequency of 50% in AMD cases and 29% in controls [odds ratio (OR) = 2.46, 95% confidence interval (1.95-3.11)]. Homozygotes for this haplotype account for 24% of cases and 8% of controls [OR = 3.51, 95% confidence interval (2.13-5.78)]. Several protective haplotypes are also identified (OR = 0.44-0.55), further implicating HF1 function in the pathogenetic mechanisms underlying AMD. We propose that genetic variation in a regulator of the alternative complement pathway, when combined with a triggering event, such as infection, underlie a major proportion of AMD in the human population.

Visual impairment caused by retinal abnormalities in mesangiocapillary (membranoproliferative) glomerulonephritis type II ("dense deposit disease")

Patients with mesangiocapillary glomerulonephritis (MCGN) type II usually present by early adulthood with hematuria, proteinuria, and renal impairment, and these features often are accompanied by a partial lipodystrophy and an autoantibody for the alternative complement pathway convertase (C3NeF). The diagnosis of MCGN type II depends on the demonstration of "dense deposits" in the glomerular basement membrane (GBM). Most patients also have multiple subretinal white spots or drusen that are histopathologically identical with the GBM deposits and evident ophthalmoscopically by the time renal failure develops. Initially visual acuity and visual fields are preserved, but fluorescein angiography and specialized tests of retinal function, such as dark adaptation, electroretinography, and electrooculography, may be abnormal and will worsen progressively. Over the next 20 years, vision often deteriorates because of retinal atrophy, and sometimes because of subretinal neovascular membranes, macular detachment, and central serous retinopathy. The authors describe a patient with MCGN type II who presented with renal failure and impaired vision at the age of 59. He already had widespread retinal atrophy, and subsequently a subretinal membrane developed. The drusen seen in MCGN type II, like the partial lipodystrophy, are a helpful clinical pointer to the diagnosis of this condition. All patients with MCGN type II should be warned of the risk of retinal complications and reviewed by an ophthalmologist at presentation and regularly after about 10 years to minimize the loss of visual acuity from complications of the retinopathy.

Structure and composition of drusen associated with glomerulonephritis: implications for the role of complement activation in drusen biogenesis

PURPOSE

The ocular fundi of many patients with membranoproliferative glomerulonephritis type II (MPGN-II) are characterised by the presence of deposits within Bruch's membrane that resemble drusen, hallmark lesions associated with age-related macular degeneration (AMD). Glomerulonephritis (GN)-associated drusen appear at a younger age, however, than do drusen in individuals with AMD. In light of recent evidence that immune-mediated events participate in drusen biogenesis and AMD, we examined the structure and composition of drusen in eyes obtained from human donors with two distinct glomerulopathies, both of which involve complement deposition within glomeruli. These features were compared with those of drusen from patients with clinically documented AMD.

METHODS

Eyes obtained from two human human donors diagnosed with membranous and post-streptococcal GN, respectively, were analysed histochemically, immunohistochemically and ultrastructurally.

RESULTS

Subretinal pigment epithelial (RPE) deposits in both types of GN are numerous and indistinguishable, both structurally and compositionally, from drusen in donors with AMD. GN-associated drusen exhibit sudanophilia, bind filipin, and react with antibodies directed against vitronectin, complement C5 and C5b-9 complexes, TIMP-3 and amyloid P component. Drusen from the membranous GN donor, but not the post-streptococcal GN donor, reacted with peanut agglutinin and antibodies directed against MHC class II antigens and IgG. The ultrastructural characteristics of these deposits were also identical with those of AMD-associated drusen.

CONCLUSIONS

The composition and structure of ocular drusen associated with membranous and post-streptococcal/segmental GN are generally similar to those of drusen in individuals with AMD. In view of the recent data supporting the involvement of complement activation in drusen biogenesis and the pathobiology of AMD, further studies of the biological relationships between AMD and diseases associated with complement activation are warranted.

Retinal function abnormalities in membranoproliferative glomerulonephritis type II

PURPOSE

To characterize retinal electrophysiologic and psychophysical abnormalities associated with membranoproliferative glomerulonephritis type II.

METHODS

Three adults with membranoproliferative glomerulonephritis type II were studied. Retinal function was measured psychophysically (automated perimetry, Farnsworth D-15 color vision testing, and dark adaptometry) and electrophysiologically (full-field flash electroretinography and electro-oculography).

RESULTS

Two symptomatic individuals had prominent drusenlike deposits and retinal pigment epithelial disturbances, findings characteristic of membranoproliferative glomerulonephritis type II retinopathy. These individuals had mild visual field and color vision abnormalities, prolonged dark adaptation, and delayed electroretinographic dark-adapted dim and bright flash responses of normal amplitude. The electro-oculogram of the most severely affected individual was abnormal. The third individual who was asymptomatic had the mildest fundus abnormalities and exhibited normal psychophysical and electrophysiologic responses.

CONCLUSIONS

Membranoproliferative glomerulonephritis type II retinopathy may be associated with symptomatic and measurable psychophysical and electrophysiologic abnormalities of retinal function.