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Anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis has diverse patterns of injury including microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Necrotizing and crescentic glomerulonephritis (NCGN) occurs in all syndromes and as renal limited vasculitis (RLV). Single-dose intravenous ANCA IgG-specific for mouse myeloperoxidase (MPO) causes RLV in mice. Although multiple mouse models have elucidated ANCA-IgG induced necrotizing and crescentic glomerulonephritis (NCGN), pathogenesis of ANCA-induced granulomatosis and vasculitis outside the kidney has not been clarified. To investigate this, we used intravenous MPO-ANCA IgG in the same strain of mice to induce different patterns of lung disease mirroring patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Repeated intravenous MPO-ANCA IgG induced GPA with NCGN, lung capillaritis, arteritis and granulomatosis. Lung leukocyte phenotypes were evaluated by immunohistochemical image analysis and by flow cytometry. ANCA lung capillaritis and microabscesses began within one day and evolved into granulomas in under seven days. Influenza plus single-dose MPO-ANCA IgG induced MPA with NCGN, lung capillaritis and arteritis, but no granulomatosis. Allergic airway disease caused by house dust mites or ovalbumin plus single-dose intravenous MPO-ANCA IgG induced EGPA with eosinophilic bronchiolitis, NCGN, capillaritis, arteritis, and granulomatosis. Thus, our study shows that the occurrence and pattern of lung lesions are determined by the same ANCA IgG accompanied by different synergistic immune factors., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Patients with microscopic polyangiitis (MPA) and positive myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA) may present with various abnormalities in chest computed tomography (CT). This study aimed to identify subphenotypes using latent class analysis (LCA) and to explore the relationship between the subphenotypes and clinical patterns, as well as compare the clinical characteristics of these subphenotypes in patients with MPO-ANCA-positive MPA (MPO-MPA)., Methods: The study identified subphenotypes using LCA based on chest CT findings in 178 patients with MPO-MPA and pulmonary involvement from June 2014 to August 2022., Results: LCA identified 27 participants (15.2%) in class 1, 43 (24.1%) in class 2, 35 (19.7%) in class 3, and 73 (41.0%) in class 4. Class 1 was characterized by prominent inflammatory exudation, class 2 by fibrosis and architectural distortion, class 3 by predominantly bronchiectasis, and class 4 by lesions mixed with inflammation and fibrosis. Class 1 had the highest level of extrapulmonary disease activity, with 77.8% of patients experiencing diffuse alveolar hemorrhage. Class 2 had the lowest level of extrapulmonary disease activity, with 41.9% of patients showing usual interstitial pneumonia. Class 3 patients were more likely to have complications involving the ear, nose, and throat, as well as pulmonary infections before treatment, and they exhibited the best outcomes. The characteristics and outcomes of class 4 were intermediate among the four classes., Conclusions: These findings suggest that bronchiectasis may represent a unique pattern of pulmonary involvement in MPO-MPA, highlighting the importance of screening for bronchiectasis in MPO-MPA and identifying optimal management strategies., Competing Interests: Declaration of competing interest The authors declared they had no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Presence of interstitial lung disease (ILD) is thought to be associated with mortality in microscopic polyangiitis (MPA); however, evidence on MPA-ILD remains lacking. Acute exacerbation (AE) refers to rapidly progressive, fatal respiratory deterioration that may develop in patients with various ILDs. No study has investigated the clinical significance of AE in MPA-ILD., Research Question: We aimed to determine the clinical picture and prognostic factors, the incidence of AE, and the risk factors in patients with MPA-ILD., Study Design and Methods: Eighty-four consecutive patients with MPA-ILD and 95 patients with MPA-non-ILD were analyzed. We also compared 80 patients with MPA-ILD and 80 patients with idiopathic interstitial pneumonia without myeloperoxidase-antineutrophil cytoplasmic antibody positivity (ILD alone), who were matched for age, sex, and chest high-resolution CT scan pattern., Results: The MPA-ILD group had a higher frequency of men and smokers and was associated with higher mortality than the MPA-non-ILD group. The matched MPA-ILD group had a higher mortality rate than the matched ILD alone group. There was no significant difference in AE incidence between the matched MPA-ILD and ILD alone groups (1-year AE cumulative incidence rate, 7.5% and 5.2%, respectively; P = .75). In the MPA-ILD group, a lower percent predicted FVC (%FVC) was independently associated with a higher mortality rate (hazard ratio [HR], 0.96 per 1% increase; P < .01) and a higher AE incidence rate (HR, 0.96 per 1% increase; P = .01). On multivariable Cox regression analysis with time-dependent covariates, developing AE during their clinical course was strongly associated with shorter survival (HR, 17.1; P < .001)., Interpretation: MPA-ILD represented a distinct phenotype with poor prognosis. Lower %FVC was an independent prognostic factor. Patients with lower %FVC had a risk of developing AE, which was a strong prognostic determinant. The specific management for MPA-ILD and AE should be established., (Copyright © 2021 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

We present the case of a 26-year-old postpartum patient who presented with an episode of desaturation and hemoptysis on postpartum day three after an uncomplicated spontaneous vaginal delivery. The patient came to our attention in the postpartum area after she experienced massive hemoptysis and we were called by the obstetric team. The patient was subsequently intubated, mechanically ventilated, and underwent bronchoscopy, demonstrating diffuse alveolar hemorrhage. She was brought to the intensive care unit, placed on high-dose steroids and plasmapheresis was initiated. Her intensive care unit course was complicated by acute respiratory distress syndrome, acute kidney injury and a pulmonary embolism, but she recovered well and was discharged on postpartum day 23. This report describes a rare case of medium vessel vasculitis diagnosed in the peripartum period, and describes the diagnostic dilemmas underlying making a rare diagnosis, and the difficulties initiating appropriate therapy in a postpartum patient., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Microscopic polyangiitis (MPA), Wegener's granulomatosis and Churg-Strauss syndrome are known as antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Cerebrovascular diseases have been rarely reported to be associated with MPA. In this study, we reported a 72-year-old man with MPA showing an initial presentation of pontine infarction, mononeuropathy multiplex and progressively deteriorating renal function. He was diagnosed with MPA on the basis of increased myeloperoxidase-specific ANCA activity, mononeuritis multiplex and the findings of renal biopsy. After receiving an aggressive treatment consisting of plasma exchange, his neurological deficit dramatically improved. For stroke patients with acute nephritis, the possibility of ANCA vasculitis should be considered. Early diagnosis may improve the prognosis.

Microscopic polyangiitis is a small vessel vasculitis which is rarely associated with ischemic stroke. Cerebrovascular disease has rarely been reported in connection with this disease. It may cause fatal hemorrhage, hemorrhagic conversion and multiple lacunar infarcts. We report here a 55-year-old woman with left medullary oblangata infarction without any symptoms of microscopic polyangiitis. During hospitalization, retinal ischemia, mononeuritis multiplex and pulmonary infiltration developed. Sural nerve biopsy was concomitant with small vessel vasculitis. Elevated CRP and sedimentation and positive P-ANCA led to confirmation of a diagnosis of microscopic polyangiitis. Our patient is a rare case of microscopic polyangiitis presenting with medullary infarction. Although the characteristics of this disease are well-known, the first symptom can be a medullary infarction, which has not been reported in literature before., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Aortic aneurysm caused by microscopic polyangiitis is very rare. It typically affects the small vessels. We report the case of a 36-year-old woman who was diagnosed with microscopic polyangiitis as a 26-year-old and who was treated with oral hydrocortisone for 10 years, and had an ascending aortic aneurysm and severe aortic insufficiency without dilatation of the sinus of Valsalva. Laboratory analysis showed high titers of serum perinuclear anti-neutrophil cytoplasmic antibodies. She underwent replacement of the ascending aorta and aortic valve on September 21, 2006. Pathologic analysis of the aneurysmal wall revealed fibrous thickening of the adventitia and intima with severe destruction and atrophy of the media. We believe that this is the first report in the literature of a surgical case of an aortic aneurysm complicated with microscopic polyangiitis.