Antineutrophil cytoplasmic antibodies and associated diseases: a review of the clinical and laboratory features

Sight-Threatening Unilateral Posterior Scleritis With Positive Atypical p-ANCA As Early Manifestation of Lupus Spectrum Disease

Antinuclear cytoplasmic antibody (ANCA)-related scleritis is a potentially sight-threatening inflammatory condition that may occur as a primary vasculitis disorder or as a secondary vasculitis in a variety of inflammatory conditions. While ANCA has been classically associated with primary vasculitis diseases such as granulomatosis with polyangiitis (GPA), microscopic polyarteritis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA), it is interesting that in cases of lupus spectrum disease (LSD), both ANCA and atypical p-ANCA have been observed as secondary autoantibodies. Scleritis is a rare ocular manifestation of lupus disease with an incidence of around 1%. This paper describes a case of sight-threatening posterior scleritis with positive atypical p-ANCA as an early manifestation of LSD. LSD is an acknowledged condition but frequently presents a diagnostic challenge or delay due to its ambiguous symptoms which may not fully align with the classification criteria of established systemic lupus erythematosus (SLE). Nonetheless, this condition should not be underestimated due to its potential impact on major organ involvement and its tendency to progress to established SLE. The diagnosis of LSD heavily relies on clinician suspicion, considering factors such as symptoms present in at least one organ system, positivity of antinuclear antibody (ANA), and clinical suspicion of future SLE development. Early identification allows for early treatment which would benefit high-risk patients. A middle-aged Chinese lady presented with bilaterally asymmetrical eye redness and swelling, which was worse on the right side. Clinical examination revealed right eye proptosis, conjunctival injection, chemosis, scleral redness and binocular diplopia in all gazes. Right eye fundoscopic examination displayed extensive choroidal folds with a positive T-sign on the B-scan. Apart from ocular symptoms, there was no significant medical history related to autoimmune or connective tissue disorders. Her p-ANCA and c-ANCA results were negative, however atypical p-ANCA titer was positive with a high antinuclear antibody (ANA) titer of 1:1280 with a homogenous pattern. Additionally, she has a family history of systemic lupus erythematosus in her daughter. A diagnosis of right eye posterior scleritis secondary to underlying LSD was made. The scleritis was successfully treated with a combination of corticosteroid and systemic immunosuppressants and the patient was initiated on oral hydroxychloroquine to manage underlying LSD. We aim to highlight to clinicians the diagnostic challenges associated with scleritis in LSD and emphasize the importance of prompt and timely multidisciplinary management in minimizing patient mortality and morbidity, as reflected in this case. This case of a positive atypical p-ANCA scleritis in LSD serves as an excellent example of effective management.

Muscle Biopsy-proven Drug-induced Microscopic Polyangiitis in a Patient with Tuberculosis

We herein report a case of muscle biopsy-proven microscopic polyangiitis (MPA) in a patient with tuberculosis. The patient had developed a persistent fever after the initiation of treatment for tuberculosis and was positive for myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA). However, because conventional symptoms were lacking, determination of the biopsy site was difficult. Based on the findings of a biopsy of the biceps femoris, which confirmed small vessel vasculitis, the patient was diagnosed with MPA. The fever was alleviated by glucocorticoids. Tuberculosis and antituberculosis drugs can cause ANCA-associated vasculitis (AAV). A muscle biopsy is useful for the diagnosis of AAV.

Syk Activation in Circulating and Tissue Innate Immune Cells in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

OBJECTIVE

Syk is a cytoplasmic protein tyrosine kinase that plays a role in signaling via B cell and Fc receptors (FcR). FcR engagement and signaling via Syk is thought to be important in antineutrophil cytoplasm antibody (ANCA) IgG-mediated neutrophil activation. This study was undertaken to investigate the role of Syk in ANCA-induced myeloid cell activation and vasculitis pathogenesis.

METHODS

Phosphorylation of Syk in myeloid cells from healthy controls and ANCA-associated vasculitis (AAV) patients was analyzed using flow cytometry. The effect of Syk inhibition on myeloperoxidase (MPO)-ANCA IgG activation of cells was investigated using functional assays (interleukin-8 and reactive oxygen species production) and targeted gene analysis with NanoString. Total and phosphorylated Syk at sites of tissue inflammation in patients with AAV was assessed using immunohistochemistry and RNAscope in situ hybridization.

RESULTS

We identified increased phosphorylated Syk at critical activatory tyrosine residues in blood neutrophils and monocytes from patients with active AAV compared to patients with disease in remission or healthy controls. Syk was phosphorylated in vitro following MPO-ANCA IgG stimulation, and Syk inhibition was able to prevent ANCA-mediated cellular responses. Using targeted gene expression analysis, we identified up-regulation of FcR- and Syk-dependent signaling pathways following MPO-ANCA IgG stimulation. Finally, we showed that Syk is expressed and phosphorylated in tissue leukocytes at sites of organ inflammation in AAV.

CONCLUSION

These findings indicate that Syk plays a critical role in MPO-ANCA IgG-induced myeloid cell responses and that Syk is activated in circulating immune cells and tissue immune cells in AAV; therefore, Syk inhibition may be a potential therapeutic option.

Diagnosing and treating ANCA-associated vasculitis: an updated review for clinical practice

ANCA-associated vasculitides (AAV) are a group of rare, primary, systemic necrotizing small-vessel vasculitides. Granulomatosis with polyangiitis and microscopic polyangiitis account for ∼80–90% of all AAV. Exposure to silica dust, farming and chronic nasal Staphylococcus aureus carriage are associated with increased risk of developing AAV. When a diagnosis of AAV is suspected, as in patients with multisystem organ dysfunction or those with features such as chronic recurrent rhinosinusitis, cavitated lung nodules, palpable purpura or acute kidney injury, then appropriate further investigations are needed, including ANCA testing. In this scenario, a structured clinical assessment should be conducted, evaluating all the organs possibly involved, and tissue biopsy may be necessary for confirmation of the diagnosis. Therapeutic algorithms vary based on the severity of AAV, the clinical diagnosis/ANCA specificity, and the patient’s age, weight, comorbidities and prognosis. Recent data favour rituximab as a preferable option for both induction and maintenance of remission. In addition, regimens with less glucocorticoids are equally effective and safer in inducing remission compared with conventional regimens, and avacopan is an effective glucocorticoid-sparing option. In contrast, there is not compelling evidence to support the routine use of plasma exchange in addition to standard remission-induction therapy in AAV. ANCA and other biomarkers can be helpful in association with clinical assessment to guide diagnosis and treatment decisions. Patients should be frequently evaluated during follow-up for possible disease relapses or treatment-related morbidity, and for monitoring damage accrual, especially metabolic and cardiovascular damage.

Granulomatosis with Polyangiitis Overlapping with IgG4-Related Disease

IgG4-related disease and granulomatosis with polyangiitis share several features as well as the presence of ANCA antibodies and serum IgG4 immunoglobulins. It is often difficult to distinguish between two entities. We hereby report the case of a patient portraying the clinical conundrum with clinical and biological features of the two diseases.

A glance into the future of anti-neutrophil cytoplasmic antibody-associated vasculitis

In the past decade, unprecedented progress has been made in understanding the pathogenesis, diagnosis, assessment, and treatment of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs). International collaborations and input from several fields (e.g. immunology, rheumatology, and nephrology) have been critical for analyzing demographics, disease manifestations, and outcomes in clinical research studies. Such efforts opened new avenues for generating novel questions and rationale to design better clinical trials. In addition, clinical research has been a source of several biological discoveries and the starting point for knowledge seeking on the pathophysiology of AAV. Interestingly, the blending of clinical and basic research provides a platform for personalized medicine. Despite recent revisions on AAV classification, the incorporation of new findings on disease genetics and immunologic responses may soon result in changes in clinical practice. These advances will enhance the selection of more specific and targeted therapies. However, current unmet needs in the management of AAV are still sizable and heavily impact long-term survival. Especially, frequent relapses, damage accrual, and high morbidity contribute to poor outcomes. Finally, the lack of defined biomarkers for disease activity and the prognosis is a permanent challenge in AAV research. Our work provides an overview of the current state of the art in AAV literature and suggests bridges for the remaining knowledge gaps. It offers potential future directions for the clinical assessment, management, and research in the field toward a more personalized medicine approach.

Laboratory Diagnosis of ANCA-Associated Vasculitis (AAV) Using a Combination of Immunofluorescence Test (IIFT) and Line Immunoassay (LIA): Single-Centre Report From India

INTRODUCTION

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated vasculitis (AAV) is a small vessel vasculitis with insufficient epidemiological estimates in India. We aimed to determine demographic, clinical features, and laboratory diagnosis of AAV patients presenting to a large tertiary care centre in India.

MATERIAL AND METHODS

1289 patient samples were screened for ANCA by indirect immunofluorescence test (IIFT) and confirmation of ANCA target antigens was done by line immunoassay. Association between IIFT and LIA was determined in AAV.

RESULTS

By IIFT, ANCA was detected in 13.0% (168 out of 1289), of which 23.8% (40/168) were positive with P-ANCA pattern, 25.0% (42/168) were positive with C-ANCA and 47.6% (80/168) showed an atypical pattern. On evaluation with a line immunoassay, 6.7% (86/1289) were positive out of which 52.3% (45/86), 41.9% (36/86), 8.8% (6/86) were positive for anti-MPO, anti-PR3, and anti-GBM respectively. In eosinophilic granulomatosis with polyangiitis (EGPA) 87.5% (7/8), and microscopic polyangiitis (MPA/RLV) 91.3% (21/23), anti-MPO was the predominantly observed antibody. In granulomatosis with polyangiitis (GPA) anti-PR3 antibody was predominant in 87.5% (28/32) cases. Out of 168 IIF positive samples 8, 32, and 23 cases of EGPA, GPA, and MPA/RLV were observed respectively.

CONCLUSIONS

The primary aim of the study was to provide single-centre data to determine the laboratory diagnosis of AAV. A combination of IIFT and LIA was found to be an optimum testing strategy for the laboratory diagnosis of AAV.

Indications and diagnostic outcome of antineutrophil cytoplasmic antibody testing in hospital medicine: a pattern of over-screening

INTRODUCTION/OBJECTIVE

Antineutrophil cytoplasmic antibodies (ANCA) serology can aid in the diagnosis and classification of ANCA-associated vasculitides (AAV). However, it is often ordered in patients without clinical manifestations of vasculitis. In this retrospective chart review, we aim to better understand the clinical practices on ANCA testing.

METHODS

We retrospectively reviewed patients' charts for the indications and diagnostic outcomes of ANCA tests. All ANCA tests ordered at two Canadian hospitals (a community hospital and an academic tertiary hospital) between January and December 2016 were included in the study. Descriptive statistics are used.

RESULTS

A total of 302 ANCA tests were included. The majority (n = 198, 65.6%) were ordered without an indication for testing. For those patients with at least 1 clinical manifestation of AAV (n = 104), 25% were ANCA positive and 18.3% resulted in a diagnosis of AAV. In comparison, among those without a clinical manifestation of AAV (n = 198), only 1.5% were ANCA positive and none was diagnosed with AAV. All patients diagnosed with AAV had at least 1 indication for ANCA testing. The three most common clinical presentations in patients with a final diagnosis of AAV were glomerulonephritis (81.8%), pulmonary hemorrhage (45.5%), and multiple lung nodules (31.8%).

CONCLUSION

To our knowledge, this is the first study that evaluates patients with both positive and negative ANCA test results in an inpatient setting. We demonstrated a low rate of ANCA positivity and AAV diagnosis in patients without clinical manifestations of AAV. Overall, there is a high rate of ANCA testing without an indication at our academic institution. This over-testing may be curbed by strategies such as a gating policy, culture changes, and clinician education. Key Points • AAV is a clinical-pathological diagnosis, and despite the usefulness of ANCA testing, it does not confirm nor rule out AAV. • ANCA testing for the diagnosis of AAV is generally only indicated when there is a clear manifestation of AAV. • Although patients with AAV may occasionally present without classic signs and symptoms, the diagnostic utility of ANCA serology in this setting is low, and testing is more likely to result in a false-positive or false-negative test. • If clinical suspicion remains high despite negative ANCA testing, clinicians should seek consultation with a rheumatologist.

IgA nephropathy with serum ANCA positivity: case series and literature review

The co-occurrence of IgA nephropathy (IgAN) and positive anti-neutrophil cytoplasmic autoantibodies (ANCA) serology is uncommon. In the present case series and literature review, we aimed to clarify the impact of ANCA on pathogenesis, clinical and histopathology presentation, and outcome in IgAN patients. We report four patients with an overlap lesion of IgAN-ANCA positive. Also, we performed a narrative review of all biopsy-proven published case series. Only 1.2% patients had ANCA in our 330-biopsy-proven IgAN cohort. We compared our data with previous reports-6 case series and 3 small retrospective studies-a total of 103 patients. All patients but one had eGFR below 15 mL/min at diagnosis. Besides rapidly decreasing eGFR, all presented with proteinuria around 1.5 g/day and dysmorphic microhematuria, suggesting glomerular inflammation. Systemic symptoms suggestive for ANCA vasculitis were seen in half of our patients, but only one patient had hemorrhagic alveolitis. Patients from our cohort responded to the intensive immunosuppressive regimens used in ANCA-positive vasculitis with renal involvement. However, in the follow-up, one patient had a relapse followed by septic shock related to immunosuppression and one patient started hemodialysis. In the review, we found that IgAN-ANCA -positive patients are characterized by vasculitis-like lesions and clinically by a rapidly progressive decline in kidney function, which was reversed by an aggressive induction immunosuppressive protocol used in ANCA vasculitis. Checking ANCA serology seems useful in patients with rapidly progressive IgAN for therapeutic and prognostic reasons.

Glomerulonephritis in AKI: From Pathogenesis to Therapeutic Intervention

Acute kidney injury (AKI) is increasingly emerging as a global emergency. Sepsis, major surgery, and nephrotoxic drugs are the main causes of AKI in hospitalized patients. However, glomerulonephritis accounts for about 10% of AKI episodes in adults, mainly related to rapidly progressive glomerulonephritis resulting from granulomatous polyangiitis (GPA, Wegener granulomatosis), microscopic polyangiitis (MPA), and anti-glomerular basement membrane (GBM) disease. Also, diffuse proliferative lupus nephritis, immunoglobulin A nephropathy, post-streptococcal glomerulonephritis, mixed cryoglobulinemia, mesangiocapillary glomerulonephritis, membranous nephropathy, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and scleroderma can induce acute renal failure. Early diagnosis of AKI due to glomerulonephritis is crucial for prompt, effective management to improve short- and long-term outcomes. Kidney biopsy is the gold standard for the diagnosis of glomerular disease, but it is not frequently performed in critically ill patients because of their clinical conditions. In this setting, a growing number of diagnostic assays can support the working hypothesis, including antineutrophil cytoplasmic antibodies (ANCAs), anti-double-stranded DNA antibodies, anti-GBM antibodies, antistreptolysin O and anti-DNase B antibodies, cryoglobulins, antiphospholipid antibodies, and complement levels. Therapeutic strategies in AKI patients with glomerulonephritis include high-dose corticosteroids, cyclophosphamide, and plasma exchange. This article reviews the wide spectrum of glomerulopathies associated with AKI, describing the immunological mechanisms underlying glomerular diseases and presenting an overview of the therapeutic options.

Acute interstitial nephritis and PR3-ANCA following reintroduction of pembrolizumab: a case report

Renal toxicity from immune checkpoint inhibitors (ICIs) is an increasingly recognized cause of acute kidney injury among patients with cancer. ICI-associated acute kidney injuries typically present as acute interstitial nephritis and the timing of onset is highly variable. Herein, we present a case of a patient with relapsed metastatic melanoma previously treated with pembrolizumab who developed grade 3 immune-related renal toxicity after reintroduction of the same ICI, secondary to acute interstitial nephritis with accompanying high PR3-antineutrophil cytoplasmic antibody titer. The patient improved after steroid treatment and discontinuation of pembrolizumab. This case highlights the importance of not excluding ICI-related nephrotoxicity as a possible cause of renal failure, including in those who previously tolerated ICI treatment, since it is a treatable entity.

Antineutrophil Cytoplasmic Antibody-Associated Glomerulonephritis in a Case of Scleroderma After Recent Diagnosis With COVID-19

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare occurrence in systemic sclerosis (SSc) patients. AAV is an inflammatory disease that can lead to kidney failure due to the infiltration of mononuclear cells and the destruction of blood vessels. Also, crescentic glomerulonephritis (GN) has rarely been reported with coronavirus disease 2019 (COVID-19) and acute tubular injury is the most common renal pathology lesion in these patients. We present a rare case of a 46-year-old woman with SSc with new onset of renal failure after a recent diagnosis of COVID-19. Her serology was positive for p-ANCA and myeloperoxidase antibodies. Kidney biopsy was done and showed crescentic GN. We suggest during this pandemic, patients with an immunological disorder that are infected with COVID-19 be closely monitored for any organ involvement.

An updated advance of autoantibodies in autoimmune diseases

Autoantibodies are abnormal antibodies which are generated by pathogenic B cells when targeting an individual's own tissue. Autoantibodies have been identified as a symbol of autoimmune disorders and are frequently considered a clinical marker of these disorders. Autoimmune diseases, including system lupus erythematosus and rheumatoid arthritis, consist of a series of disorders that share some similarities and differences. They are characterized by chronic, systemic, excessive immune activation and inflammation and involve in almost all body tissues. Autoimmune diseases occur more frequently in women than men due to hormonal impacts. In this review we systemically introduce and summarize the latest advances of various autoantibodies in multiple autoimmune diseases.

Frequency of Positive ANCA Test in a Population With Clinical Symptoms Suggestive of Autoimmune Disease and the Interference of ANA in its Interpretation

BACKGROUND

Antibodies against neutrophil cytoplasm (ANCA) are associated with vasculitis. There are different methods to determine their presence. The interference of antinuclear antibodies (ANA) in the differentiation between P-ANCA and C-ANCA patterns has been described.

OBJECTIVE

To determine the frequency of ANCA in a population with manifestations of autoimmune disease, and evaluate the interference of ANA in its interpretation.

MATERIALS AND METHODS

Retrospective, descriptive nonexperimental cross-sectional study, including 3,330 data. The presumptive diagnosis was autoimmune disease and a test for ANCA was requested. The ANCA and ANA determinations were made by indirect immunofluorescence, L-ANCA® and CytoBead® ANCA. Anti-proteinase 3 and anti-myeloperoxidase were detected by ELISA and CytoBead® ANCA.

RESULTS

ANCAs were positive in 10.21% and 12.64% of those positive for ANCA were positive for ANA. The inter-rater agreement statistic (Kappa) for anti-PR3 between CytoBead ANCA and ELISA was 100% (K=1.00; P<.05) and the agreement between anti- myeloperoxidase by ELISA and CytoBead® ANCA was high (K=0.94; P<.05). 30% of those with ANCAs had a diagnosis of a type of vasculitis; 20% of them had an autoimmune disease.

CONCLUSIONS

The results suggest an overestimated request for ANCAs as a diagnostic aid in primary care which was not addressed. For an adequate evaluation of ANCAs, the indirect immunofluorescence technique should be implemented for the control and confirmation with the determination of specific antigens for anti- proteinase 3 and anti- myeloperoxidase in any of the confirmatory assays. The high concordance shown by ANCA CytoBeads makes us consider the use of this alternative for the determination of ANCAs and the confirmation. Given the interference of ANAs, the ANA test by IFI in the presence of positive P-ANCA results is recommended in order to minimize "false positives".

Laboratory Diagnosis of ANCA-Associated Vasculitis (AAV) Using a Combination of Immunofluorescence Test (IIFT) and Line Immunoassay (LIA): Single-Centre Report From India

INTRODUCTION

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated vasculitis (AAV) is a small vessel vasculitis with insufficient epidemiological estimates in India. We aimed to determine demographic, clinical features, and laboratory diagnosis of AAV patients presenting to a large tertiary care centre in India.

MATERIAL AND METHODS

1289 patient samples were screened for ANCA by indirect immunofluorescence test (IIFT) and confirmation of ANCA target antigens was done by line immunoassay. Association between IIFT and LIA was determined in AAV.

RESULTS

By IIFT, ANCA was detected in 13.0% (168 out of 1289), of which 23.8% (40/168) were positive with P-ANCA pattern, 25.0% (42/168) were positive with C-ANCA and 47.6% (80/168) showed an atypical pattern. On evaluation with a line immunoassay, 6.7% (86/1289) were positive out of which 52.3% (45/86), 41.9% (36/86), 8.8% (6/86) were positive for anti-MPO, anti-PR3, and anti-GBM respectively. In eosinophilic granulomatosis with polyangiitis (EGPA) 87.5% (7/8), and microscopic polyangiitis (MPA/RLV) 91.3% (21/23), anti-MPO was the predominantly observed antibody. In granulomatosis with polyangiitis (GPA) anti-PR3 antibody was predominant in 87.5% (28/32) cases. Out of 168 IIF positive samples 8, 32, and 23 cases of EGPA, GPA, and MPA/RLV were observed respectively.

CONCLUSIONS

The primary aim of the study was to provide single-centre data to determine the laboratory diagnosis of AAV. A combination of IIFT and LIA was found to be an optimum testing strategy for the laboratory diagnosis of AAV.

False Positive COVID-19 Antibody Test in a Case of Granulomatosis With Polyangiitis

Collateral damage due to 2019 novel coronavirus disease (COVID-19) represents an emerging issue. Symptoms of COVID-19 are not disease-specific. Differential diagnosis is challenging and the exclusion of other life-threatening diseases has major caveats. In the era of this pandemic, diagnosis of other life-threatening diseases might delay treatment. The Food and Drug Administration has recently authorized the first antibody-based test for COVID-19; however, RT-PCR of nasopharyngeal or oropharyngeal swabs remains the recommended test for diagnosis. We present the first report of a false positive COVID-19 antibody test in a case of Granulomatosis with Polyangiitis (GPA). Specifically, the case concerns an 82-year-old female, never smoker, who was admitted to our hospital with symptoms of fever and general fatigue that had lasted 7 days. She already had a positive IgM test for COVID-19, yet multiple RT-PCR tests had returned as negative for SARS-CoV-2. In the following days, her renal function deteriorated, while hematuria and proteinuria with active urinary sediment developed. Based on high clinical suspicion for ANCA-associated vasculitis, we performed a complete immunologic profile which revealed positive c-ANCA with elevated titers of anti-PR3. Pulses of methylprednisolone along with cyclophosphamide were applied. At day 10, treatment response was noticed as indicated by respiratory and renal function improvement. This report highlights the need for meticulous patient evaluation in order to avoid misdiagnosis in the era of COVID-19.

A Comparison of Immunoglobulin Variable Region N-Linked Glycosylation in Healthy Donors, Autoimmune Disease and Lymphoma

N-linked glycans play an important role in immunity. Although the role of N-linked glycans in the Fragment crystallizable (Fc) region of immunoglobulins has been thoroughly described, the function of N-linked glycans present in Ig-variable domains is only just being appreciated. Most of the N-linked glycans harbored by immunoglobulin variable domain are of the complex biantennary type and are found as a result of the presence of N-linked glycosylation that most often have been introduced by somatic hypermutation. Furthermore, these glycans are ubiquitously present on autoantibodies observed in some autoimmune diseases as well as certain B-cell lymphomas. For example, variable domain glycans are abundantly found by anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) as well as by the B-cell receptors of follicular lymphoma (FL). In FL, variable domain glycans are postulated to convey a selective advantage through interaction with lectins and/or microbiota, whereas the contribution of variable domain glycans on autoantibodies is not known. To aid the understanding how these seemingly comparable phenomena contribute to a variety of deranged B-responses in such different diseases this study summarizes the characteristics of ACPA and other auto-antibodies with FL and healthy donor immunoglobulins, to identify the commonalities and differences between variable domain glycans in autoimmune and malignant settings. Our finding indicate intriguing differences in variable domain glycan distribution, frequency and glycan composition in different conditions. These findings underline that variable domain glycosylation is a heterogeneous process that may lead to a number of pathogenic outcomes. Based on the current body of knowledge, we postulate three disease groups with distinct variable domain glycosylation patterns, which might correspond with distinct underlying pathogenic processes.

Comparison between enzyme-linked immunosorbent assay and indirect immunofluorescence for detection of antineutrophil cytoplasmic antibodies

Objective

To evaluate the performance of enzyme-linked immunosorbent assay and indirect immunofluorescence methods for the detection of antineutrophil cytoplasmic antibodies in a routine clinical laboratory setting.

Methods

A total of 227 samples were tested by indirect immunofluorescence and enzyme-linked immunosorbent assay with antigen specificity for antiproteinase 3 and antimyeloperoxidase. The proportions of positive samples were compared by McNemar hypotheses and agreement was described by Cohen’s Kappa coefficient.

Results

The agreement of the tests was 96.5%, and the Kappa coefficient obtained was 0.70 (95%CI: 0.50-0.90; p<0.001). Considering indirect immunofluorescence as the gold standard, the sensitivity of the enzyme-linked immunosorbent assay was 0.62 and the specificity was 0.99, with diagnostic accuracy in 96% of cases. Some samples were negative in enzyme-linked immunosorbent assay and positive in indirect immunofluorescence. This situation occurred in all immunofluorescence patterns, but particularly in atypical patterns. Two samples with antiproteinase 3 positivity were considered negative in indirect immunofluorescence.

Conclusion

The enzyme-linked immunosorbent assay had high specificity but lower sensitivity. The performance of indirect immunofluorescence increases diagnostic sensitivity, while the search for antiproteinase 3 by enzyme-linked immunosorbent assay may also add diagnostic power.

Saint John on Patmos: Revelations of the Role of Antineutrophil Cytoplasmic Antibody (ANCA) in Vasculitis

Diagnosis of vasculitis is based on the presence of histologic features and serological testing for antineutrophil cytoplasmic antibodies (ANCA). In patients with vasculitis, two types of ANCA have been identified: ANCA directed against the neutrophil serine protease proteinase-3 (PR3) which results in a cytoplasmic immunofluorescence pattern (c-ANCA) and ANCA directed against the neutrophil enzyme myeloperoxidase (MPO), which results in a perinuclear immunofluorescence pattern (p-ANCA). Question is if the presence of ANCA is the consequence of abnormal neutrophil adhesion, activation, and apoptosis. Or is it, through mechanisms which are not totally clear for the moment, the cause of vasculitis. In the latter case it has to be postulated that ANCA autoantigens are expressed on the cell surface of viable, or activated, or early-apoptotic neutrophils.

Granulomatosis with polyangiitis in a patient with biopsy-proven IgG4-related pulmonary disease and coincident small cell lung cancer

Granulomatosis with polyangiitis (GPA) was diagnosed in a patient with a 16-month history of IgG4-related lung disease that spontaneously became asymptomatic. Cytoplasmic antineutrophil cytoplasmic antibody (ANCA) was positive at the time of diagnosis of IgG4-related disease (IgG4-RD), but there was no vasculitis or kidney disease. Sixteen months later he developed rapidly progressive glomerulonephritis that responded to cyclophosphamide treatment. While undergoing treatment for GPA, he was found to have a lung mass identified as small cell lung cancer. This mass was present at the time of the IgG4-RD diagnosis. GPA can be confused with IgG4-RD histologically and they rarely coexist. ANCA antibodies are primarily IgG4 subclass. IgG4-RD has been associated with cancer and may improve prognosis. We speculate that this patient may have had small cell lung cancer that incited an IgG4 predominant immune response with coexistent ANCA antibodies that eventually resulted in GPA. Immunosuppressive treatment of GPA likely accelerated the progression of the lung cancer.

Immunoglobulins G from patients with ANCA-associated vasculitis are atypically glycosylated in both the Fc and Fab regions and the relation to disease activity

Background

Anti-neutrophil cytoplasmic autoantibodies (ANCA) directed against myeloperoxidase (MPO) and proteinase 3 (PR3) are pathogenic in ANCA-associated vasculitis (AAV). The respective role of IgG Fc and Fab glycosylation in mediating ANCA pathogenicity is incompletely understood. Herein we investigate in detail the changes in Fc and Fab glycosylation in MPO-ANCA and Pr3-ANCA and examine the association of glycosylation aberrancies with disease activity.

Methodology

Total IgG was isolated from serum or plasma of a cohort of 30 patients with AAV (14 MPO-ANCA; 16 PR3-ANCA), and 19 healthy control subjects. Anti-MPO specific IgG was affinity-purified from plasma of an additional cohort of 18 MPO-ANCA patients undergoing plasmapheresis. We used lectin binding assays, liquid chromatography, and mass spectrometry-based methods to analyze Fc and Fab glycosylation, the degree of sialylation of Fc and Fab fragments and to determine the exact localization of N-glycans on Fc and Fab fragments.

Principal findings

IgG₁ Fc glycosylation of total IgG was significantly reduced in patients with active AAV compared to controls. Clinical remission was associated with complete glycan normalization for PR3-ANCA patients but not for MPO-ANCA patients. Fc-glycosylation of anti-MPO specific IgG was similar to total IgG purified from plasma. A major fraction of anti-MPO specific IgG harbor extensive glycosylation within the variable domain on the Fab portion.

Conclusions/Significance

Significant differences exist between MPO and PR3-ANCA regarding the changes in amounts and types of glycans on Fc fragment and the association with disease activity. These differences may contribute to significant clinical difference in the disease course observed between the two diseases.

Pulmonary disorders that are potentially associated with anti- neutrophilic cytoplasmic antibodies: A brief review

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis frequently manifests with involvement of the lungs and kidneys, and it also may affect other anatomic sites. This article presents the patterns of pulmonary injury in which ANCA-associated vasculitis is included in the differential diagnosis, with a discussion of antineutrophil cytoplasmic antibody testing methods. The histologic features of non-vasculitic, potentially-ANCA-associated pulmonary lesions are reviewed briefly as well.

Value of non-identified ANCA (non-PR3, non-MPO) in the diagnosis of granulomatosis with polyangiitis (Wegener's granulomatosis)

OBJECTIVE

Determine the frequency of granulomatosis with polyangiitis (GPA) associated with non-identified ANCA (non-MPO, non-PR3 ANCA) and secondarily compare their clinic with GPA associated with MPO-positive or PR3-positive ANCA.

METHODS

In a monocentric retrospective observational study, clinical data of 398 patients with non-identified ANCA (titer of ANCA at least 1/80 by immunofluorescence on ethanol fixed PMN) was gathered over a period of 6 years. GPA patients from this population were compared with GPA patients with identified ANCA on the basis of clinical, biological, immunological and histological features.

RESULTS

The most common diseases associated with non-identified ANCA were inflammatory bowel diseases accounting for 17% of diseases. GPA accounted for only 1.8% of cases. There were no significant differences in terms of clinical and histological characteristics between GPA with non-identified ANCA and GPA with identified ANCA, but significantly higher CRP levels were observed in GPA patients with identified ANCA (p = 0.005). Localized disease (ear, nose and throat and/or lung involvement without any other systemic involvement) was more frequent in the group of GPA with nonidentified ANCA (p = 0.047) as compared to GPA with identified ANCA. This explains that the former group of patients was less frequently treated by cyclophosphamide than the latter (p = 0.016).

CONCLUSION

GPA with non-MPO, non-PR3 ANCAs is relatively rare. Our study suggests that GPA with nonidentified ANCA differs from GPA with identified ANCA by the frequency of localized forms.

Discrepancies between two immunoassays for the determination of MPO and PR3 autoantibodies

BACKGROUND

Testing for autoantibodies to myeloperoxidase (MPO) and proteinase 3 (PR3) is part of anti-neutrophil cytoplasmic antibodies (ANCA) test that aids the diagnosis of a number of autoimmune diseases including small-vessel vasculitis. We characterized the differences between two automated immunoassays at three facilities for measuring MPO- and PR3-ANCA autoantibodies.

METHODS

117 serum samples were analyzed for MPO and PR3 autoantibodies. The INOVA QUANTA Lite® IgG assay (INOVA Diagnostics) were performed at two facilities and the Bio-Plex® 2200 Vasculitis Panel (Bio-Rad) were performed at a third reference lab. The results were compared both qualitatively (between INOVA QUANTA Lite® and Bio-Plex® methods) and quantitatively (between two sites performing INOVA QUANTA Lite® assays).

RESULTS

Comparison of the INOVA QUNATA Lite® assays at two different facilities (n=36) demonstrated high concordance (97.2% for MPO and 94.4% for PR3) and quantitative correlation (R²=0.973 for MPO and R²=0.935 for PR3). Conversely, INOVA QUNATA Lite® and Bio-Plex® methods showed poor concordance at 70.4% for MPO (n=81; 95% CI: 59.7% to 79.2%) and at 76.5% for PR3 (n=81; 95% CI: 66.2% to 84.4%).

CONCLUSION

This study demonstrated low concordance between two methods for MPO-ANCA and PR3-ANCA measurements. Given the discrepancies, the performance of different autoantibody immunoassay methods should be taken into consideration when evaluating MPO-ANCA and PR3-ANCA results.

Onset of Microscopic Polyangiitis in Binephrectomied Patient on Chronic Hemodialysis-Case Report

Introduction

Microscopic polyangiitis (MPA) is one of the causes of the pulmonary–renal syndrome associated with elevated non-specific markers of inflammation and antineutrophil cytoplasmic autoantibody (ANCA) positivity in 50–75%. De novo occurrence of the disease in patients on chronic hemodialysis (HD) has not been described.

Case presentation

We presented patient who developed MPO-ANCA-associated MPA with lung and musculoskeletal involvement after 4 years on regular HD due to bilateral nephrectomy. After excluding the other causes of MPO-ANCA positivity, diagnosis was confirmed even without renal biopsy. Patient received standard immunosuppression therapy and he is still in remission after 27 months.

Conclusion

The onset of immune-mediated disease could be observed even after introduction of renal replacement therapy, which may be a diagnostic problem. Early recognition and traditional immunosuppressive regiment may provide successful outcome.

Simultaneous comprehensive multiplex autoantibody analysis for rapidly progressive glomerulonephritis

Rapidly progressive glomerulonephritis (RPGN) is mainly caused by anti-glomerular basement membrane (GBM) antibody-mediated glomerulonephritis, immune-complex or anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides and leads to rapid loss of renal function. Detection of ANCA and autoantibodies (autoAbs) to GBM and dsDNA enables early diagnosis and appropriate treatment of RPGN aiding in preventing end-stage renal disease.Determination of ANCA on neutrophils (ANCA) as well as autoAbs to myeloperoxidase (MPO-ANCA), proteinase 3 (PR3-ANCA), GBM, and dsDNA was performed by the novel multiplex CytoBead technology combining cell- and microbead-based autoAb analyses by automated indirect immunofluorescence (IIF). Forty patients with granulomatosis with polyangiitis (GPA), 48 with microscopic polyangiitis (MPA), 2 with eosinophilic GPA, 42 with systemic lupus erythematosus (SLE), 43 with Goodpasture syndrome (GPS), 57 with infectious diseases (INF), and 55 healthy subjects (HS) were analyzed and findings compared with classical single testing.The CytoBead assay revealed for GPA, MPA, GPS, and SLE the following diagnostic sensitivities and for HS and INF the corresponding specificities: PR3-ANCA, 85.0% and 100.0%; MPO-ANCA, 77.1% and 99.1%; anti-GBM autoAb, 88.4% and 96.4%; anti-dsDNA autoAb, 83.3% and 97.3%; ANCA, 91.1% and 99.1%, respectively. Agreement with classical enzyme-linked immunosorbent assay and IIF was very good for anti-GBM autoAb, MPO-ANCA, PR3-ANCA, and ANCA, respectively. Anti-dsDNA autoAb comparative analysis demonstrated fair agreement only and a significant difference (P = 0.0001).The CytoBead technology provides a unique multiplex reaction environment for simultaneous RPGN-specific autoAb testing. CytoBead RPGN assay is a promising alternative to time-consuming single parameter analysis and, thus, is well suited for emergency situations.

Recent advances in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis is an uncommon inflammatory disease of small to medium-sized vessels that frequently presents with rapidly progressive glomerulonephritis and renal failure though it can affect any organ system. If untreated, the vast majority of patients will die within a year. Current treatments improve prognosis but affected patients remain at a substantially higher risk of death and adverse outcomes. We review the classification of the disease, our understanding of the pathogenesis and epidemiology, and propose future directions for research. We also evaluate the evidence supporting established treatment regimens and the progress of clinical trials for newer treatments to inform the design of future studies.

Granulomatosis with Polyangiitis (Wegener's Granulomatosis) Accompanied by Dysuria

A 65-year-old male visited us with complaints of retarded urination, dysuria, gross hematuria, and fever. Urinalysis showed pyuria. Prostatic tumor with lung metastasis was suspected from computed tomography and magnetic resonance imaging. Transurethral prostatic biopsy and bronchoscopic biopsy only revealed fibrinoid necrosis and inflammatory infiltration. Right lateral maxillary sinusitis was also found by MRI. ANCA testing was positive with specificity for anti-PR3 (PR3-ANCA). On the basis of these results, Granulomatosis with polyangiitis (GPA) was diagnosed. GPA involving the prostate gland is unusual, and only a few cases have previously been reported.

Enzyme-labeled Antigen Method: Development and Application of the Novel Approach for Identifying Plasma Cells Locally Producing Disease-specific Antibodies in Inflammatory Lesions

In chronic inflammatory lesions of autoimmune and infectious diseases, plasma cells are frequently observed. Antigens recognized by antibodies produced by the plasma cells mostly remain unclear. A new technique identifying these corresponding antigens may give us a breakthrough for understanding the disease from a pathophysiological viewpoint, simply because the immunocytes are seen within the lesion. We have developed an enzyme-labeled antigen method for microscopic identification of the antigen recognized by specific antibodies locally produced in plasma cells in inflammatory lesions. Firstly, target biotinylated antigens were constructed by the wheat germ cell-free protein synthesis system or through chemical biotinylation. Next, proteins reactive to antibodies in tissue extracts were screened and antibody titers were evaluated by the AlphaScreen method. Finally, with the enzyme-labeled antigen method using the biotinylated antigens as probes, plasma cells producing specific antibodies were microscopically localized in fixed frozen sections. Our novel approach visualized tissue plasma cells that produced 1) autoantibodies in rheumatoid arthritis, 2) antibodies against major antigens of Porphyromonas gingivalis in periodontitis or radicular cyst, and 3) antibodies against a carbohydrate antigen, Strep A, of Streptococcus pyogenes in recurrent tonsillitis. Evaluation of local specific antibody responses expectedly contributes to clarifying previously unknown processes in inflammatory disorders.

Increase of Antimyeloperoxidase Antineutrophil Cytoplasmic Antibody (ANCA) in Patients with Renal ANCA-associated Vasculitis: Association with Risk to Relapse

Objective.

The diagnostic values of antiproteinase 3 and antimyeloperoxidase tests using antineutrophil cytoplasmic antibodies (ANCA) are well established. Our study determined whether an increase in ANCA level was a predictor of disease flareup.

Methods.

Our study included 126 patients with ANCA-associated renal vasculitis treated at 9 nephrology centers in Japan. The relationship between increased ANCA levels and relapse was assessed using time-dependent multivariate Cox regression models adjusted for clinically relevant factors. The outcome of interest was the time from remission to first relapse.

Results.

During the observation period [median 41 mos, interquartile range (IQR) 23–66 mos], 118 patients (95.8%) achieved remission at least once. After achieving remission, 34 patients relapsed (21.7%). Time-dependent multivariate Cox regression models revealed that lung involvement (adjusted HR 2.29, 95% CI 1.13–4.65, p = 0.022) and increased ANCA levels (adjusted HR 17.4, 95% CI 8.42–36.0, p < 0.001) were significantly associated with relapse. The median time from ANCA level increase to relapse was 0.6 months (IQR 0–2.1 mos).

Conclusion.

In our study, an increase in ANCA level during remission was associated with a risk of disease relapse. A rise in ANCA level may be useful for guiding treatment decisions in appropriate subsets of patients with ANCA-associated vasculitis.

Higher Antineutrophil Cytoplasmic Antibody (C-ANCA) Titers are Associated with Increased Overall Healthcare Use in Patients with Sinonasal Manifestations of Granulomatosis with Polyangiitis (GPA)

Background

Granulomatosis with polyangiitis (GPA) is an autoimmune disease characterized by necrotizing granulomatous airway inflammation and vasculitis. Sinonasal involvement occurs in more than 80% cases, with antineutrophil cytoplasmic antibody (C-ANCA) titers used as a marker of disease severity. The purpose of this study was to determine whether C-ANCA levels impact radiographic findings and healthcare use in patients with sinonasal GPA.

Methods

A retrospective review was performed on GPA patients evaluated in a multidisciplinary rheumatologic/otolaryngologic clinic from 2008 to 2013. Data were collected with respect to age, gender, clinical presentation, C-ANCA titers, Lund-Mackay (LM) scores, surgical interventions, and healthcare use, the latter of which were determined by assessing the number of rheumatology/otolaryngology clinic visits, computed tomography (CT) scans, and email/telephone encounters.

Results

A total of 44 patients were identified, 11 male and 33 female. Sinonasal manifestations were evident in 70.4%, with chronic rhinosinusitis (CRS) (41.9%), septal perforation (38.7%), and crusting (32.2%) the most common findings. No significant differences in number of CT scans (p = 0.10) or mean LM scores (p = 0.47) were found between patients with more than or equal to 1:80 and less than 1:80 C-ANCA titers, respectively. However, overall healthcare use was increased in the more than or equal to 1:80 C-ANCA group (n = 28) compared with less than 1:80 (n = 16), with a significantly greater number of rheumatologic/otolaryngologic encounters (mean 121 versus 69.2, p = 0.03) noted. When otolaryngologic healthcare use was specifically examined, the average number of encounters was also higher in more than or equal to 1:80 C-ANCA patients (31.9 versus 22.9), but this difference was not statistically significant (p = 0.16).

Conclusion

Sinonasal GPA patients with presenting C-ANCA titers more than or equal to 1:80 demonstrated significantly greater overall healthcare use than their lower C-ANCA level counterparts (less than 1:80). However, no significant differences in otolaryngology resource use or LM scores were evident between the two titer groups.

Protein microarrays: a new tool for the study of autoantibodies in immunodeficiency

Autoimmunity is highly coincident with immunodeficiency. In a small but growing number of primary immunodeficiencies, autoantibodies are diagnostic of a given disease and implicated in disease pathogenesis. In order to improve our understanding of the role of autoantibodies in immunodeficiencies and to discover novel autoantibodies, new proteomic tools are needed. Protein microarrays have the ability to screen for reactivity to hundreds to many thousands of unique autoantigens simultaneously on a single chip using minimal serum input. Here, we review different types of protein microarrays and how they can be useful in framing the study of primary and secondary immunodeficiencies.

Clinical aspects of indirect immunofluorescence for autoimmune diseases

Because the most common term used in conversations considering autoimmunity is autoantibodies, it is well-expected that the indirect immunofluorescence assay, which detects antibodies directed against various antigens, is one of our most impressive techniques for investigating autoimmune diseases (AIDs). Roughly speaking, the current literature corroborates that this immunopathologic investigation means that autoantibodies detection makes a considerable contribution to both diagnostic and prognostic aspects of AIDs in the clinical setting. However, it varies between different AIDs, autoantibodies, ethnicities or detection methodologies. Directly focusing on the indirect immunofluorescence assay, we present evidence to support this multidimensional variation regarding the subject via reviewing briefly the best-investigated autoantibodies in the well-documented AIDs, including vasculitis, inflammatory bowel disease, scleroderma, autoimmune hepatitis, primary biliary cirrhosis, systemic lupus erythematosus and Sjögren's syndrome.

B-cell therapy in antineutrophil cytoplasmic antibody-associated vasculitis

Until recently, standard of care for patients with generalized or severe antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) has consisted of an induction regimen with cyclophosphamide (CYC) and corticosteroids followed by maintenance treatment with azathioprine. This regimen is associated with significant toxicity resulting in considerable morbidity and mortality whereas relapses are still not infrequent. In two controlled trials, the Rituximab in ANCA-associated Vasculitis study (RAVE) and the RITUXVAS trial of the European Vasculitis Study Group (EUVAS), rituximab (RTX) proved non-inferior to CYC for induction of remission. In addition, outcome at 18 months for the RAVE trial and 12 months for the RITUXVAS trial showed that RTX without maintenance treatment was as efficacious as CYC followed by azathioprine maintenance. To prevent relapses, which occur particularly in patients positive for PR3-ANCA, 500 mg RTX given every 6 months was shown to be superior to azathioprine in a French study. Thus, RTX is a new and promising therapeutic armamentarium for AAV although long-term safety has still to be established.

Simultaneous automated screening and confirmatory testing for vasculitis-specific ANCA

Anti-neutrophil cytoplasmic antibodies (ANCA) are the serological hallmark of small vessel vasculitis, so called ANCA-associated vasculitis. The international consensus requires testing by indirect immunofluorescence (IIF) on human ethanol-fixed neutrophils (ethN) as screening followed by confirmation with enzyme-linked immunosorbent assays (ELISAs). This study evaluates the combination of cell- and microbead-based digital IIF analysis of ANCA in one reaction environment by the novel multiplexing CytoBead technology for simultaneous screening and confirmatory ANCA testing. Sera of 592 individuals including 118 patients with ANCA-associated vasculitis, 133 with rheumatoid arthritis, 49 with infectious diseases, 77 with inflammatory bowel syndrome, 20 with autoimmune liver diseases, 70 with primary sclerosing cholangitis and 125 blood donors were tested for cytoplasmic ANCA (C-ANCA) and perinuclear ANCA (P-ANCA) by classical IIF and ANCA to proteinase 3 (PR3) and myeloperoxidase (MPO) by ELISA. These findings were compared to respective ANCA results determined by automated multiplex CytoBead technology using ethN and antigen-coated microbeads for microbead immunoassays. There was a good agreement for PR3- and MPO-ANCA and a very good one for P-ANCA and C-ANCA by classical and multiplex analysis (Cohen's kappa [κ] = 0.775, 0.720, 0.876, 0.820, respectively). The differences between classical testing and CytoBead analysis were not significant for PR3-ANCA, P-ANCA, and C-ANCA (p<0.05, respectively). The prevalence of confirmed positive ANCA findings by classical testing (IIF and ELISA) compared with multiplex CytoBead analysis (IIF and microbead immunoassay positive) resulted in a very good agreement (κ = 0.831) with no significant difference of both methods (p = 0.735). Automated endpoint-ANCA titer detection in one dilution demonstrated a very good agreement with classical analysis requiring dilution of samples (κ = 0.985). Multiplexing by CytoBead technology can be employed for simultaneous screening and quantitative confirmation of ANCA. This novel technique provides fast and cost-effective ANCA analysis by automated digital IIF for the first time.

Antineutrophil cytoplasmic antibody frequency in chronic hepatitis B patients

Background. Chronic hepatitis B (CHB) is a viral disease, common across the world, and associated with several extraintestinal manifestations including vasculitis. Antineutrophil cytoplasmic antibodies (ANCAs) are sensitive and specific markers for vasculitides. There is limited data available in the literature on whether ANCA formation is stimulated by CHB infection. In the present study we aimed to identify the frequency of ANCA in CHB patients. Methods. A total of 174 subjects were included in the study (87 CHB patients, 87 control subjects). Perinuclear-ANCA (P-ANCA), cytoplasmic-ANCA (C-ANCA), myeloperoxidase ANCA (MPO-ANCA), and proteinase 3-ANCA (PR3-ANCA) were studied. IFA was used for P-ANCA and C-ANCA assays, and ELISA was used for MPO-ANCA and PR3-ANCA assays. Results. ANCA positivity was high in both groups (31% in the CHB group and 26% among controls). There were no significant differences between the groups for P-ANCA and MPO-ANCA (P = 0.6 and P = 0.6, resp.). Frequency of borderline positive C-ANCA and all positive PR3-ANCA (positive + borderline positive) was significantly higher in the CHB group (P = 0.009 and P = 0.005, resp.). Conclusions. In the present study, the frequency of ANCA was high in both groups. The CHB group had a relatively higher frequency of ANCA positivity compared to controls. Borderline positive C-ANCA and positive PR3-ANCA were significantly higher in the CHB group. These results suggest that ANCA may have a high prevalence in Turkey. Patients with CHB should be evaluated particularly for C-ANCA and PR3-ANCA in the presence of vasculitic complaints and lesions.

Pulmonary renal syndrome in a child with coexistence of anti-neutrophil cytoplasmic antibodies and anti-glomerular basement membrane disease: case report and literature review

BACKGROUND

Pulmonary renal syndrome (PRS), denoting the presence of diffuse alveolar hemorrhage and glomerulonephritis as manifestations of systemic autoimmune disease, is very rare in childhood. The coexistence of circulating anti-neutrophil cytoplasmic antibody (ANCA) and anti-glomerular basement membrane (GBM) disease in children affected by this syndrome is exceptional, with unfavorable outcome in five out of seven patients reported to date. We describe a child with PRS associated with both circulating anti-myeloperoxidase (anti-MPO) ANCA and anti-GBM disease on renal biopsy who was successfully treated with immunosuppressive therapy.

CASE PRESENTATION

A 10-year old girl presented with fever, fatigue, malaise, and pallor followed by hemoptysis and severe anemia. Diffuse alveolar hemorrhage was revealed on fiberoptic bronchoscopy. Renal findings consisted of microscopic hematuria, moderate proteinuria, and anti-GBM disease on renal biopsy. ANCA with anti-MPO specificity were present whereas anti-GBM antibodies were on borderline for positivity. Methyl-prednisolone pulses followed by prednisone led to cessation of hemoptysis, marked improvement of lung fuction, and normal finding on chest x-ray within 10 days. An immunosuppressive regimen was then given consisting of prednisone daily for 4 weeks with subsequent taper on alternate day, i.v. cyclophosphamide pulses monthly for 6 doses, followed by mycophenolate mofetil that resulted in normal lung function tests, hemoglobin concentration, and anti-MPO level within four subsequent weeks. During 10-months of follow-up she remained well, her blood pressure and renal function tests were normal, and proteinuria and hematuria gradually resolved.

CONCLUSION

We report a child with an exceptionally rare coexistence of circulating ANCA and anti-GBM disease manifesting as PRS in whom renal disease was not the prominent part of clinical presentation, contrary to other reported pediatric patients. A review of literature on disease with double positive antibodies is also presented. Evaluation of a patient with PRS should include testing for presence of different antibodies. An early diagnosis and rapid institution of aggressive immunosuppressive therapy can induce remission and preserve renal function. Renal prognosis depends on the extent of kidney injury at diagnosis and appropriate treatment.

Automated indirect immunofluorescence evaluation of antinuclear autoantibodies on HEp-2 cells

Indirect immunofluorescence (IIF) on human epithelial (HEp-2) cells is considered as the gold standard screening method for the detection of antinuclear autoantibodies (ANA). However, in terms of automation and standardization, it has not been able to keep pace with most other analytical techniques used in diagnostic laboratories. Although there are already some automation solutions for IIF incubation in the market, the automation of result evaluation is still in its infancy. Therefore, the EUROPattern Suite has been developed as a comprehensive automated processing and interpretation system for standardized and efficient ANA detection by HEp-2 cell-based IIF. In this study, the automated pattern recognition was compared to conventional visual interpretation in a total of 351 sera. In the discrimination of positive from negative samples, concordant results between visual and automated evaluation were obtained for 349 sera (99.4%, kappa = 0.984). The system missed out none of the 272 antibody-positive samples and identified 77 out of 79 visually negative samples (analytical sensitivity/specificity: 100%/97.5%). Moreover, 94.0% of all main antibody patterns were recognized correctly by the software. Owing to its performance characteristics, EUROPattern enables fast, objective, and economic IIF ANA analysis and has the potential to reduce intra- and interlaboratory variability.

Anti-neutrophil cytoplasmic autoantibodies: methodological aspects and clinical significance in systemic vasculitis

Antineutrophil cytoplasmic antibodies (ANCA) are the serological hallmark of some idiopathic systemic vasculitides, such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and, to a lesser extent, Churg-Strauss syndrome (CCS), the so-called ANCA-associated vasculitides (AAV). ANCA were first detected by immunofluorescence (IIFT), subsequently the target antigens myeloperoxidase (MPO) and proteinase 3 (PR3) were identified, allowing the development of the quantitative, antigen-specific assays. According to the guidelines, combining IIFT and PR3-ANCA/MPO-ANCA assures the optimal diagnostic specificity. Antigen specificity does not effectively differentiate among the different AAV, however C-ANCA/PR3-ANCA are mainly found in GPA, while P-ANCA/MPO-ANCA are more prevalent in MPA and CSS. Despite their diagnostic value, the performance of the widespread immunometric assays for ANCA testing is disappointing, particularly for the low sensitivity. In recent years, more "sensitive" assays have been developed, using the microplate as well as fully the automated technologies, with promising preliminary results. ANCA, may be detected in a number of pathological conditions other than small vessel vasculitis. However, in most of these non-vasculitic patients ANCA do not recognize MPO or PR3 as target antigens, but other granulocyte components, often multiple or unknown specificities. A positive ANCA result by itself is not diagnostic for AAV, clinical evidence and possibly histological confirmation are always required. On the other hand, a negative test result cannot completely rule out a diagnosis of AAV, as AAV without detectable ANCA exist. The appropriate use of ANCA testing strongly improves the diagnostic accuracy and clinical usefulness of the results.

PR3 antibodies do not induce renal pathology in a novel PR3-humanized mouse model for Wegener's granulomatosis

Different murine models have been used as basis for Proteinase 3 (PR3)-associated vasculitis models, but sufficient reproduction of the human clinical manifestation has failed to this date. As a reliable animal model is needed to further elucidate the pathological value of PR3-ANCA, we developed a PR3-humanized transgenic mouse model, in order to induce a glomerulonephritis. Our huPR3-transgenic mice were injected i.v. with our monoclonal antibodies, either unlabeled or directly labeled by fluorescein isothiocyanate. For a period of 5 days, proteinuria and erythrocyte count were measured with urine dip sticks. None of the mice exhibited proteinuria and/or an abnormal number of erythrocytes in the urine. Five days after antibody treatment, the mice were killed and different organs were fixed and immunohistochemically assessed. In the case of the kidney, we could detect a glomerulonephritis. Our study is able to show that although a direct renal target was given in transgenic human PR3 mice, no renal pathology was detectable. Multifactorial mechanisms for PR3-ANCA involvement in the development of Wegener's granulomatosis must be hypothesized.

Crescentic Glomerulonephritis: an update on Pauci-immune and Anti-GBM diseases

Crescentic glomerulonephritis (GN) in a renal biopsy is a widely accepted "critical diagnosis" in Anatomic Pathology practice. Prompt biopsy evaluation and notification of the referring physician is essential to facilitate rapid therapeutic intervention. The differential diagnostic categories of crescentic GN include pauci-immune GN, anti-glomerular basement membrane (GBM) nephritis and immune complex-mediated GN, distinguished from one another by immunofluorescence and electron microscopic study of the renal biopsy. Immune complex-mediated GN is characterized by abundant glomerular deposits and encompasses several diseases including but not limited to lupus nephritis, cryoglobulinemic GN and immunoglobulin A nephropathy. Pauci-immune GN, with paucity of deposits, correlates closely with antineutrophil cytoplasmic antibody disease due to the identifiable circulating pathogenic antineutrophil cytoplasmic antibody in most patients. Recent studies have identified other antibodies in pauci-immune GN and implicated infectious organisms in triggering autoimmunity in a susceptible host by molecular mimicry of host antigens. Anti-GBM nephritis is a rare but potentially life-threatening autoimmune disease with circulating antibodies against GBM epitopes in α3 chain of type IV collagen. It is characterized by a linear immunoglobulin G deposition along GBM on immunofluorescence microscopy. Environmental triggers including infections and solvent exposure seem to change the tertiary structure of the type IV collagen α345 hexamer in GBM, expose neoepitopes, and initiate autoimmunity. Even in light of advances in understanding of pathophysiology and serologic testing, renal biopsy remains the mainstay of diagnosis of crescentic GN.

Propylthiouracil-induced antineutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis versus primary ANCA-associated renal vasculitis: a comparative study

OBJECTIVE

Renal involvement is frequently present in primary antineutrophil cytoplasmic antibody-associated small-vessel vasculitis (AAV) as well as propylthiouracil (PTU)-induced AAV. We analyzed the characteristics of patients with PTU-induced AAV with renal involvement and investigated the differences of the 2 diseases.

METHODS

Thirty-six patients with PTU-induced AAV, diagnosed from 1997 to 2010, were enrolled for study. Their data were compared with those of 174 patients with primary AAV diagnosed at the same time. Renal involvement was present in all patients.

RESULTS

There was a prominent proportion of young women with PTU-induced AAV (p < 0.01). They had lower levels of proteinuria and serum creatinine and higher estimated glomerular filtration rate (p < 0.01, p < 0.01, and p < 0.01, respectively). Clinical immunological abnormalities were less severe in patients with PTU-induced AAV. Patients with PTU-induced AAV had less organ involvement and lower Birmingham Vasculitis Assessment Score than patients with primary AAV (p < 0.01). Renal biopsies showed a lower proportion of glomeruli with crescents (p < 0.01). Interstitial inflammation was less severe in patients with PTU-induced AAV (p < 0.05). Similarly, interstitial fibrosis and tubular atrophy were less severe in patients with PTU-induced AAV (p < 0.01, p < 0.05, respectively). Renal survival and total survival were better in patients with PTU-associated vasculitis (p < 0.05, p = 0.01).

CONCLUSION

Clinical and histopathological abnormalities were less severe in patients with PTU-induced AAV and most of them had a good prognosis.