Crescentic glomerulonephritis and subepidermal blisters with autoantibodies to alpha5 and alpha6 chains of type IV collagen

Coexistence of anti-glomerular basement membrane disease and IgA nephropathy: an illustrative case and comprehensive literature review

Anti-glomerular basement membrane (GBM) disease is a rare autoimmune condition characterized by the presence of positive anti-GBM autoantibodies, linear deposition of immunoglobulin G (IgG) along the GBM and severe kidney injury. In a limited number of cases, the association of anti-GBM disease with other glomerulonephritis has been reported. Herein, we present the case of a 66-year-old female patient with progressive worsen kidney function and decreased urine output. A renal biopsy revealed crescent glomerulonephritis with lineal IgG deposition along the GBM and mesangial IgA deposition, which supported the diagnosis of concurrent anti-GBM disease and IgA nephropathy (IgAN). In an extensive literature review, we identified a total of thirty-nine patients were reported anti-GBM disease combined with IgAN. The clinical characteristics of these patients demonstrate that the anti-GBM disease combined with IgAN tends to be milder with a more indolent course and a better prognosis than the classic anti-GBM disease, and its potential pathogenesis deserves to be further explored.

Denovo glomerulonephritis associated with IgA anti-GBM alloantibodies after kidney transplantation in Alport syndrome: A case report with diagnostic implications

Alport syndrome (AS) is a hereditary disorder caused by pathogenic variants in COL4A3, COL4A4, or COL4A5 genes expressing α3, α4, and α5 chains of basement membrane type IV collagen (COL4). The triple-helical α3α4α5(IV) protomer is a major component of the mature glomerular basement membrane (GBM) whose defective formation in AS leads to structural GBM disruption and kidney dysfunction, often resulting in kidney replacement therapy. A genetically intact renal graft exposes the immune system to a non-tolerized α3α4α5(IV) component and an alloimmune response eventually ensues. So far, only IgG alloantibodies reacting against COL4 have been reported in AS alloimmune responses. Here, we report alloimmune glomerulonephritis mediated by IgA antibodies against the non-collagenous C-terminal domain 1 of the α5(IV) chain in a patient with autosomal recessive AS following a second kidney transplantation. The patient presented a not previously described biallelic variant in the COL4A4 gene. Immunological, diagnostic, and clinical implications are discussed.

The Prevalence and Characteristics of Circulating IgA Anti-Glomerular Basement Membrane Autoantibodies in Anti-Glomerular Basement Membrane Disease

Introduction

In some cases, immunoglobulin (IgA)-mediated antiglomerular basement membrane (anti-GBM) disease has been reported. Whether circulating IgA anti-GBM antibodies affect the clinico-pathologic characteristics and outcome of typical anti-GBM disease deserves further study.

Methods

Circulating IgA anti-α3(IV)NC1 antibodies were examined by enzyme-linked immunosorbent assay (ELISA) using recombinant human α3(IV)NC1 as solid phase antigens in 107 patients with anti-GBM disease and 115 controls. Clinical, pathological, and follow-up data of patients were retrospectively analyzed.

Results

Circulating IgA anti-α3(IV)NC1 antibodies were found in 18.7% (20/107) of patients with anti-GBM disease but were not detected in healthy controls or in patients with other glomerular diseases. The positivity of circulating IgA anti-α3(IV)NC1 antibodies was not associated with whether the patient was with combined IgA nephropathy or other glomerulonephritis. Kidney immunofluorescence showed no statistical difference in IgA deposition between patients with circulating IgA anti-α3(IV)NC1 antibodies and patients without (30.0% vs. 40.4%, P = 0.725). The titers of circulating immunoglobulin G (IgG) anti-α3(IV)NC1 antibodies in patients with circulating IgA anti-α3(IV)NC1 antibodies were significantly higher than those without (200 [183.3, 200] vs. 161 [85.5, 200] U/ml, P = 0.005). There were no significant differences in kidney outcome and mortality between the 2 groups.

Conclusion

Circulating IgA anti-α3(IV)NC1 antibodies occurred in 18.7% (20/107) of patients with anti-GBM in our center and were specific to anti-GBM disease. Patients with circulating IgA anti-α3(IV)NC1 antibodies showed a higher levels of serum IgG anti-α3(IV)NC1 antibodies than those without.

Bullous Pemphigoid in X-linked Alport Syndrome

Skin lesions in X-linked Alport syndrome (XLAS) are rarely observed. Bullous pemphigoid (BP) is caused by autoantibodies against BP180, also called α1 (XVII) chain, in the basement membrane zone (BMZ). A 48-year-old man with XLAS developed tense blisters. A skin biopsy showed a cleft between the basal cell layer and dermis, with the infiltration of neutrophils and eosinophils. α1 (XVII) staining was positive on the epidermal side of α2/5 (IV) staining. Oral prednisolone improved his symptoms gradually. Abundant tense blisters on the palms and soles might suggest an important role of the α5 (IV) chain in the integrity of BMZ.

Alport Syndrome and Oral Mucous Membrane Pemphigoid: An Interesting Case

Alport syndrome (AS) is a hereditary progressive glomerular disease associated with sensorineural hearing loss and ocular abnormalities. It is attributed to the altered structure and the subsequent dysfunction of the glomerular basement membrane (GBM) due to the mutated type IV collagen a3/a4/a5 chains. It may emerge either as an X-linked disease, the most common, or as an autosomal disease, both recessive and dominant. A female patient, 26 years old, came in 2023 to the Department of Oral Medicine/ Pathology, Dental School, Aristotle University of Thessaloniki, complaining about pain and a burning sensation in her right cheek. Her medical history revealed the diagnosis of Alport syndrome in 2016 and kidney transplantation in 2022 with extensive post-transplantation drug administration. The clinical examination revealed an ulcer, partially covered by a pseudomembrane, on the oral mucosa of the right cheek, surrounded by an erythematous border. A biopsy was taken, and the histopathological examination showed the oral manifestation of mucous membrane pemphigoid. After communicating with the attending nephrologist, the prescription of methylprednisolone was decided, and the lesions receded. The differential diagnosis included both AS-induced pemphigoid and drug-induced pemphigoid. The thorough medical history, detailed clinical investigation, lesion biopsy, and collaboration of different dental and medical specialties constitute necessary prerequisites for a successful treatment, even in immunosuppressed patients.

Atypical Anti-Glomerular Basement Membrane Disease

Atypical anti-glomerular basement membrane (anti-GBM) disease is characterized by linear immunoglobulin G (IgG) deposition along the GBM without circulating IgG anti-GBM antibodies. Compared to classic anti-GBM disease, atypical anti-GBM disease tends to be milder with a more indolent course in certain cases. Moreover, pathologic disease pattern is much more heterogenous in atypical anti-GBM disease than in the classic type, which is uniformly characterized by diffuse crescentic and necrotizing glomerulonephritis. Although there is no single well-established target antigen in atypical anti-GBM disease, the target antigen (within the GBM) and the autoantibody type are hypothesized to be different from the classic type. Some patients have the same antigen as the Goodpasture antigen that are detected only by a highly sensitive technique (biosensor analysis). Some cases of atypical anti-GBM disease have autoantibodies of a different subclass restriction like IgG4, or of monoclonal nature. Antibodies targeting antigen/epitope structure other than the Goodpasture antigen can be detected using modified assays in some cases. Patients with IgA- and IgM-mediated anti-GBM disease are known to have negative circulating antibodies because conventional assays do not detect these classes of antibodies. A significant proportion of cases with atypical anti-GBM disease do not have any identifiable antibodies despite extensive evaluation. Nevertheless, extensive evaluation of atypical autoantibodies using modified assays and sensitive techniques should be attempted, if feasible. This review summarizes the recent literature on atypical anti-GBM disease.

5-Fluorouracil With Microneedling Modulates Wound Healing in a Murine Model: An Immunohistochemical Analysis of Mechanism and Dose Efficacy

PURPOSE

The purpose of this study is to assess the dose-dependent immunohistopathological effects of intradermal microneedle-delivered 5-fluorouracil (5-FU) for postincisional wound healing in a murine model.

METHODS

A prospective experimental study was performed. Twelve hairless mice were randomized into 4 treatment groups for postincisional wound treatment: microneedling with topical saline, or microneeding with topically-applied 5-FU at concentrations of 25 mg/ml, 50 mg/ml, or 100 mg/ml. Two surgical wounds were created on each animal. Combination wound treatments were performed on postoperative days 14 and 28, and cutaneous biopsies were obtained on day 56. Specimens were analyzed by a dermatopathologist, blinded to the treatment group, for collagen thickness, lymphocytic infiltration, histiocytic response, sub-epidermal basement membrane zone thickness, and myofibroblast density.

RESULTS

Histopathologic evaluation showed increased collagen thickness, lymphocyte infiltration, and granuloma density in the groups undergoing microneedling treatment with 5-FU, compared to saline. Immunohistochemical analysis revealed a trend toward thicker basement membranes with higher concentrations of 5-FU used, reaching statistical significance between controls and those treated with 100 mg/ml 5-FU ( p = 0.0493). A trend toward decreasing myofibroblast density with increasing doses of 5-FU was noted. No postincisional or treatment complications were observed.

CONCLUSIONS

Our results demonstrate that microneedling is an effective topical subepithelial drug delivery system, and further suggest a beneficial dose-dependent immunomodulatory effect of 5-FU on intermediate wound healing when used in combination with microneedling. We recommend a 5-FU dose at the mid-range 50 mg/ml concentration to simultaneously maximize efficacy and minimize complication risk.

Suppression of collagen IV alpha-2 subunit by prolyl hydroxylase domain inhibition via hypoxia-inducible factor-1 in chronic kidney disease

Elevation of hypoxia-inducible factor 1 protein has been shown to be protective in acute kidney injury and HIF1α enhancing drug therapies are currently in clinical trials for the treatment of anemia of chronic kidney disease. Despite its benefits, long-term HIF1 elevation seems to be associated with additional effects in the kidneys such as tubulointerstitial fibrosis. To better understand the effects of prolonged HIF1 exposure, assessment of baseline and post-therapy levels of HIF1α and other related biomarkers is essential. In this study, we assessed the effect of HIF1α enhancement using prolyl hydroxylase inhibitor (PHD-I) DMOG, on a key profibrotic marker of kidney disease. In specific, we examined the change in expression of Collagen 4 subunit A2 in cultured urinary cells of CKD patients pre and post 24-hour exposure to 1mM DMOG. Our results show that besides HIF1α enhancement, COL4A2 protein is suppressed in presence of DMOG. To determine if this effect is mediated by HIF1, we used HIF1α gene silencing in HEK293 cells and examined the effect of DMOG on protein and gene expression of COL4A2 post 24-hour exposure. We showed that silencing HIF1α reverses and amplifies the expression of COL4A2 in HEK293 cells. Our data suggest that HIF1 directly regulates the expression of COL4A2 in kidney cells and that HIF1α enhancing therapy has suppressive effects on COL4A2 that may be clinically relevant and must be considered in determining the safety and efficacy of these drugs in the treatment of anemia.

Diagnostic and management challenges in Goodpasture's (anti-glomerular basement membrane) disease

Goodpasture's or anti-glomerular basement membrane (GBM) disease is classically characterized by the presence of circulating autoantibodies directed against the non-collagenous domain of the α3 chain of type IV collagen, targeting glomerular and alveolar basement membranes, and associated with rapidly progressive crescentic glomerulonephritis, with alveolar haemorrhage in over half the patients. However, there are increasing examples of variants or atypical presentations of this disease, and novel therapeutic options have been proposed, which nephrologists should be aware of. The pathophysiology of this condition has been understood through molecular analysis of the antibody-antigen interactions and the use of human leucocyte antigen-transgenic animals, while the association of anti-GBM antibodies with anti-neutrophil cytoplasm antibodies and their combined impact on disease phenotype is increasingly recognized, providing some insights into the basis of glomerular damage and autoimmunity.

Patients affected by a new variant of endemic pemphigus foliaceus have autoantibodies colocalizing with MYZAP, p0071, desmoplakins 1-2 and ARVCF, causing renal damage

BACKGROUND

We have previously reported that about 30% of patients affected by a new variant of endemic pemphigus foliaceus (EPF) in El Bagre, Colombia (termed El Bagre-EPF or pemphigus Abreu-Manu) have systemic compromise. In the current study, we focused on studying autoreactivity to the kidney and its pathological correlations.

AIM

To investigate patients with El Bagre-EPF for renal compromise.

METHODS

We performed a case-control study, enrolling 57 patients with El Bagre-EPF and 57 controls from the endemic area, matched by age, sex, race, work activity, demographics and comorbidities. We took skin and renal biopsies; performed direct and indirect immunofluorescence, immunohistochemistry (IHC), confocal microscopy, immunoblotting, direct and indirect immune electron microscopy; and tested kidney function in all living patients. We also used IHC to study seven kidney autopsy samples.

RESULTS

Of the 57 patients, 19 had autoantibodies to kidney, with polyclonal reactivity (P < 0.01). Most cases were positive along the basement membrane of the proximal tubules, but in some cases there was also positivity against the glomeruli and/or mixed patterns. Fifteen patients had increases in serum urea and creatinine compared with controls (P < 0.01). The autoantibodies colocalized with commercial antibodies to desmoplakins I and II, p0071, armadillo repeat gene deleted in velo-cardio-facial syndrome (ARCVF) and myocardium-enriched zonula occludens-1-associated protein (MYZAP) (P < 0.01). All of the kidney disease autopsies showed alterations, mostly in the vessels.

CONCLUSION

We demonstrate for the first time that one-third of patients with El Bagre-EPF have polyclonal autoantibodies to kidney. The kidneys showed a mixed histological pattern resembling lupus nephritis, with a diffuse proliferative Class IV (G) global diffuse pattern in active lesions, and additional interposition of membranoproliferative glomerulonephritis.

Minor collagens of the skin with not so minor functions

The structure and function of the skin relies on the complex expression pattern and organisation of extracellular matrix macromolecules, of which collagens are a principal component. The fibrillar collagens, types I and III, constitute over 90% of the collagen content within the skin and are the major determinants of the strength and stiffness of the tissue. However, the minor collagens also play a crucial regulatory role in a variety of processes, including cell anchorage, matrix assembly, and growth factor signalling. In this article, we review the expression patterns, key functions and involvement in disease pathogenesis of the minor collagens found in the skin. While it is clear that the minor collagens are important mediators of normal tissue function, homeostasis and repair, further insight into the molecular level structure and activity of these proteins is required for translation into clinical therapies.

Basement membranes and autoimmune diseases

Basement membrane components are targets of autoimmune attack in diverse diseases that destroy kidneys, lungs, skin, mucous membranes, joints, and other organs in man. Epitopes on collagen and laminin, in particular, are targeted by autoantibodies and T cells in anti-glomerular basement membrane glomerulonephritis, Goodpasture's disease, rheumatoid arthritis, post-lung transplant bronchiolitis obliterans syndrome, and multiple autoimmune dermatoses. This review examines major diseases linked to basement membrane autoreactivity, with a focus on investigations in patients and animal models that advance our understanding of disease pathogenesis. Autoimmunity to glomerular basement membrane type IV is discussed in depth as a prototypic organ-specific autoimmune disease yielding novel insights into the complexity of anti-basement membrane immunity and the roles of genetic and environmental susceptibility.

Antibodies to α5 chain of collagen IV are pathogenic in Goodpasture's disease

Autoantibody against glomerular basement membrane (GBM) plays a direct role in the initiation and development of Goodpasture's (GP) disease. The principal autoantigen is the non-collagenous domain 1 (NC1) of α3 chain of collagen IV, with two immunodominant epitopes, EA-α3 and EB-α3. We recently demonstrated that antibodies targeting α5NC1 are bound to kidneys in GP patients, suggesting their pathogenic relevance. In the present study, we sought to assess the pathogenicity of the α5 autoantibody with clinical and animal studies. Herein, we present a special case of GP disease with circulating autoantibody reactive exclusively to the α5NC1 domain. This autoantibody reacted with conformational epitopes within GBM collagen IV hexamer and produced a linear IgG staining on frozen sections of human kidney. The antibody binds to the two regions within α5NC1 domain, EA and EB, and inhibition ELISA indicates that they are targeted by distinct sub-populations of autoantibodies. Sequence analysis highlights five residues that determine specificity of antibody targeting EA and EB epitopes of α5NC1 over homologous regions in α3NC1. Furthermore, immunization with recombinant α5NC1 domain induced crescentic glomerulonephritis and alveolar hemorrhage in Wistar-Kyoto rats. Thus, patient data and animal studies together reveal the pathogenicity of α5 antibodies. Given previously documented cases of GP disease with antibodies selectively targeting α3NC1 domain, our data presents a conundrum of why α3-specific antibodies developing in majority of GP patients, with α5-specific antibodies emerged in isolated cases, the answer for which is critical for understanding of etiology and progression of the GP disease.

IgA-mediated anti-glomerular basement membrane disease: an uncommon mechanism of Goodpasture's syndrome

Goodpasture's (GP) disease is usually mediated by IgG autoantibodies. We describe a case of IgA-mediated GP, in a patient presenting with isolated rapidly progressive glomerulonephritis. The diagnosis was established on kidney biopsy, since routine enzyme-linked immunosorbent assay (ELISA) targeted at IgG circulating autoantibodies failed to detect the nephritogenic antibodies. Immunofluorescence microscopy showed intense linear deposition of IgA along the glomerular capillary walls. An elevated titre (1:80) of circulating IgA anti-glomerular basement membrane (GBM) antibodies was retrospectively demonstrated by indirect fluorescence. Despite immunosuppressive regimen, the disease progressed to end-stage renal failure (ESRF). Transplantation was not associated with recurrence in the kidney graft. We reviewed the 11 previously reported cases of IgA-mediated GP.

Collagen IV in Normal Skin and in Pathological Processes

CONTEXT

Type IV collagen is a type of collagen found primarily in the skin within the basement membrane zone. The type IV collagen C4 domain at the C-terminus is not removed in post-translational processing, and the fibers are thus link head-to-head, rather than in a parallel fashion. Also, type IV collagen lacks a glycine in every third amino-acid residue necessary for the tight collagen helix. Thus, the overall collagen-IV conformation is structurally more pliable and kinked, relative to other collagen subtypes. These structural features allow collagen IV to form sheets, which is the primary structural form found in the cutaneous basal lamina. There are six human genes associated with collagen IV, specifically COL4A1, COL4A2, COL4A3, COL4A4, COL4A5 and COL4A6. The aim of this review is to highlight the significance of this protein in normal skin, and in selected diseases.

RESULTS

The alpha 3 protein constituent of type IV collagen is thought to be the antigen implicated in Goodpasture's syndrome, wherein the immune system attacks the basement membranes of the renal glomeruli and pulmonary alveoli. In addition, mutations to the genes coding for type IV collagen lead to the Alport syndrome. Furthermore, autoantibodies directed against denatured human type IV collagen have been described in rheumatoid arthritis, scleroderma, and SLE. Structural studies of collagen IV have been utilized to differentiate between subepidermal blistering diseases, including bullous pemphigoid, acquired epidermolysis bullosa, anti-epiligrin cicatricial pemphigoid, and bullous lupus erythematosus. Collagen IV is also of importance in wound healing and in embryogenesis.

CONCLUSIONS

Pathological studies have demonstrated that minor structural differences in collagen IV can lead to distinct, clinically different diseases.

Antigenic heterogeneity of IgA anti-GBM disease: new renal targets of IgA autoantibodies

Anti-glomerular basement membrane (anti-GBM) disease is an aggressive form of glomerulonephritis, usually mediated by immunoglobulin G (IgG) autoantibodies to the noncollagenous (NC1) domain of alpha 3(IV) collagen. Less is known about the target antigen(s) in patients with atypical anti-GBM disease involving IgA autoantibodies. We report a new case of IgA anti-GBM disease in a patient with a history of proliferative lupus nephritis who presented with increasing creatinine levels, proteinuria, and hematuria, but no clinical or serological evidence of lupus recurrence. Renal biopsy showed focal and segmental necrotizing glomerulonephritis with strong linear capillary loop IgA staining by means of immunofluorescence. Serological test results were negative for IgG or IgA autoantibodies against the alpha 3NC1 domain. By means of immunoblotting, IgA from patient serum bound to 38- to 48-kd antigens collagenase-solubilized from human GBM, but not to purified NC1 domains of GBM collagen IV. The target of patient's IgA autoantibodies thus was identified as a novel GBM antigen, distinct from the alpha 3NC1 domain or other known targets of anti-GBM IgA autoantibodies. Clinical resolution was attained by means of conventional treatment with steroids and cyclophosphamide. The diversity of antigens recognized by anti-GBM IgA autoantibodies highlights the importance of renal biopsy for the reliable diagnosis of this rare condition because conventional serological immunoassays likely would yield false-negative results.

Linear IgA disease of childhood developing IgA nephropathy

We report the case of a 10-year-old girl presenting with linear IgA disease of childhood who in the follow-up at age 16 developed hematuria and proteinuria resulting from IgA nephropathy. The combination of linear IgA disease and Berger nephropathy appears to be extremely uncommon but clinical alertness to this association might discover additional cases.