Dual anti-neutrophil cytoplasmic antibody-related pauci-immune crescentic glomerulonephritis in a patient with Sjögren's syndrome

Dual MPO/PR3 ANCA positivity and vasculitis: insights from a 7-cases study and an AI-powered literature review

OBJECTIVES

Anti-neutrophil cytoplasm antibodies (ANCA)-associated vasculitides (AAV) are rare conditions characterized by inflammatory cell infiltration in small blood vessels, leading to tissue necrosis. While most patients with AAV present antibodies against either myeloperoxidase (MPO) or proteinase 3 (PR3), rare cases of dual positivity for both antibodies (DP-ANCA) have been reported, and their impact on the clinical picture remains unclear. The goal of this study was to investigate the clinical implications, phenotypic profiles and outcomes of patients with DP-ANCA.

METHODS

A retrospective screening for DP-ANCA cases was conducted at Brest University Hospital's immunology laboratory (France), analysing ANCA results from March 2013 to March 2022. Clinical, biological, imaging, and histological data were collected for each DP-ANCA case. Additionally, a comprehensive literature review on DP-ANCA was performed, combining an artificial intelligence (AI)-based search using BIBOT software with a manual PUBMED database search.

RESULTS

The report of our cases over the last 9 years and those from the literature yielded 103 described cases of patients with DP-ANCA. We identified four distinct phenotypic profiles: (i) idiopathic AAV (∼30%); (ii) drug-induced AAV (∼25%); (iii) autoimmune disease associated with a low risk of developing vasculitis (∼20%); and (iv) immune-disrupting comorbidities (infections, cancers, etc) not associated with AAV (∼25%).

CONCLUSION

This analysis of over a hundred DP-ANCA cases suggests substantial diversity in clinical and immunopathological presentations. Approximatively 50% of DP-ANCA patients develop AAV, either as drug-induced or idiopathic forms, while the remaining 50%, characterized by pre-existing dysimmune conditions, demonstrates a remarkably low vasculitis risk. These findings underscore the complex nature of DP-ANCA, its variable impact on patient health, and the necessity for personalized diagnostic and management approaches in these cases.

Serum ANCA as Disease Biomarkers: Clinical Implications Beyond Vasculitis

Usually associated with autoimmune diseases, anti-neutrophil cytoplasmic antibodies are also detected in other conditions, such as infections, malignancies, and after intake of certain drugs. Even if the mechanisms of production and their pathogenic role have not been fully elucidated yet, ANCA are widely recognized as a clinically alarming finding due to their association with various disorders. While ANCA target several autoantigens, proteinase-3, and myeloperoxidase are the ones proved to be most frequently related to chronic inflammation and tissue damage in murine models. Albeit these autoantibodies could be present as an isolated observation without any implications, ANCA are frequently used in clinical practice to guide the diagnosis in a suspect of small vessel vasculitis. Conditions that should prompt the clinician to test ANCA status range from various forms of lung disease to renal or peripheral nervous system impairment. ANCA positivity in the presence of an autoimmune disease, especially rheumatoid arthritis, or connective tissue diseases, is frequently correlated with more clinical complications and treatment inefficacy, even in the absence of signs of vasculitis. For this reason, it has been postulated that ANCA could represent the final expression of an immune dysregulation rather than a pathogenic event responsible for organs damage. Recently, it has also been proposed that ANCA specificity (PR3 or MPO) could possibly define ANCA-associated vasculitides better than clinical phenotype. This review aims at summarizing the latest advancements in the field of ANCA study and clinical interpretation.

Can antineutrophil cytoplasmic antibody positivity at diagnosis predict the poor outcomes of Sjögren's syndrome?

We investigated the clinical implication of ANCA positivity at diagnosis on the poor outcomes in patients with Sjögren's syndrome. The medical records of 606 Korean patients with Sjögren's syndrome were retrospectively reviewed. The results of perinuclear (P)-ANCA, myeloperoxidase (MPO)-ANCA, cytoplasmic (C)-ANCA, and proteinase 3 (PR3)-ANCA were collected and the frequencies of all-cause mortality, interstitial lung disease (ILD), end-stage renal disease (ESRD), and lymphoma were assessed as the poor outcomes of Sjögren's syndrome. Comparison of the cumulative patient survivals between the two groups was analysed by the Kaplan-Meier survival analysis. Of the 606 patients, ANCA was detected in 10.2% of Sjögren's syndrome patients without AAV. Twenty-one patients (3.5%) died, 99 patients (16.3%) suffered from ILD, and 8 patients had ESRD. Lymphoma occurred in 5 patients (0.8%) during 37.5 months. Sjögren's syndrome patients with ANCA positivity exhibited a lower cumulative ILD-free survival rate than those with ANCA negativity (P = 0.001). Sjögren's syndrome patients with P-ANCA positivity and those with MPO-ANCA (or P-ANCA) positivity showed a lower cumulative ILD-free survival rate than those without (P = 0.012 and P < 0.001). Also, Sjögren's syndrome patients with P-ANCA positivity exhibited a lower cumulative ESRD-free survival rate than those without (P = 0.043). ANCA positivity was associated with neither all-cause mortality nor lymphoma in Sjögren's syndrome patients. ANCA positivity and MPO-ANCA (or P-ANCA) positivity at diagnosis was associated with the development of ILD during follow-up in patients with Sjögren's syndrome.

Emergence of Smoldering ANCA-associated Glomerulonephritis during the Clinical Course of Mixed Connective Tissue Disease and Sjögren's Syndrome

A 67-year-old woman presented with hematuria and proteinuria 16 and 11 months ago, respectively. She had been followed up as mixed connective tissue disease and Sjögren's syndrome for over 19 years. Blood chemistry showed no elevated serum creatinine or C-reactive protein but did reveal myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) of 300 U/dL. A kidney biopsy showed pauci-immune focal necrotizing glomerulonephritis. She was treated with prednisolone and rituximab, resulting in normal urinalysis and decreased MPO-ANCA. The complication of ANCA-associated glomerulonephritis should not be overlooked when abnormal urinalysis findings appear in the course of connective tissue disease, irrespective of the presence of rapidly progressive glomerulonephritis.