ANCA-associated glomerulonephritis is one of the most serious manifestations of ANCA-associated vasculitis, a group of autoimmune conditions in which the body produces antibodies against proteins normally found in neutrophils, the rapidly responding white blood cells that form the first line of defense against infection. When these autoantibodies bind neutrophils, they can push the cells into a destructive state in which they attack the small blood vessels of the kidney’s filtering units, the glomeruli. The resulting inflammation destroys kidney tissue and can progress rapidly to organ failure. Although treatment options have improved in recent years, current therapies rely heavily on broad immunosuppression, which carries risks ranging from serious side effects of prolonged use to outright treatment failure.

Lead author Masayuki Nishide explains why the kidney makes such a valuable window into the autoimmune process. In ANCA-associated glomerulonephritis, the kidneys are frequently involved, which makes the organ an excellent candidate for studying the initial steps of the autoimmune disease sequence. Yet until now, little was known about the order of events that unfold in the earliest phase of the disease, precisely the stage at which an intervention could prevent the most damage.

To reconstruct that sequence, the researchers compared kidney samples from healthy donors with samples from patients with ANCA-associated glomerulonephritis who had not yet received treatment. Using spatial transcriptomics, a cutting-edge technology that reads out gene activity across a tissue while preserving the physical organization of the cells, they studied the progression of the disease in its native cellular context. This approach matters because autoimmune injury is not just about which cells are present but about where they sit relative to one another, and conventional methods that break tissue apart lose exactly that information.

The comparison produced a striking result. Diseased kidneys showed more cellular damage than normal ones, but the changes went deeper than expected. Senior author Atsushi Kumanogoh notes that the team was surprised to find that even in tissue that appeared normal under standard examination, changes could still be detected at the cellular level. The goal, he says, was to investigate exactly how the disease unfolds in the early stage so that it could be stopped before significant damage is done.

The spatial maps revealed a specific pathogenic architecture. Injured proximal tubular epithelial cells, the kidney cells that line the tubules and perform much of the organ’s reabsorptive work, send out signals that attract immune cells, including neutrophils. The accumulating neutrophils cluster around the damaged epithelial cells, forming a local microenvironment the researchers term a neutrophil–epithelial niche. Within this niche, the two cell populations reinforce each other: the injured epithelial cells recruit and stimulate the neutrophils, and the activated neutrophils drive the spread of inflammation through the surrounding kidney tissue. Excessive neutrophil activation emerged as a key feature of early disease, positioning these cells not as innocent bystanders but as central engines of the injury process.

That insight suggested a specific molecular target. Neutrophil activation in this disease depends on Fcγ receptors, the cell-surface proteins that recognize the tail region of antibodies and translate antibody binding into cellular responses. In ANCA-associated glomerulonephritis, stimulation of Fcγ receptors by the disease autoantibodies is integral to the development of the inflammatory process. The researchers therefore engineered modified antibodies designed to minimize stimulation of these receptors, aiming to dampen neutrophil activation without eliminating the cells altogether.

To test the approach, the team replicated the kidney injury in a mouse model of the disease and treated the animals with the modified antibodies. The results were promising: the engineered antibodies successfully reduced kidney injury in the model. By quieting the Fcγ receptor signals that fuel neutrophil activation, the treatment appears to act on the mechanism that drives the earliest phase of the disease, rather than on downstream inflammation that has already caused tissue destruction.

The findings point to a potential new therapeutic strategy aimed at stopping ANCA-associated glomerulonephritis at its earliest stage, before severe kidney damage develops. Because the approach targets a defined step in the disease mechanism, it could in principle offer patients safer treatments with fewer side effects than the broad immunosuppressive regimens used today. The researchers hope that continued development in this area can translate the mouse-model results into clinical benefit, giving patients new options at the stage of disease where intervention matters most.

The study, titled Epitope-diverse autoantibodies induce neutrophil–epithelial niches driving kidney injury in ANCA-associated glomerulonephritis, involved collaboration with Chugai Pharmaceutical Co., Ltd. Several co-authors are employees of and shareholders in the company, and Atsushi Kumanogoh has received grant support from Chugai Pharmaceutical. The work was conducted at the Immunology Frontier Research Center of the University of Osaka using human tissue samples alongside the experimental mouse studies, and it was published in the Journal of Experimental Medicine with the DOI 10.1084/jem.20260506.

Subject of Research: ANCA-associated glomerulonephritis early disease mechanism and modified antibody treatment

Article Title: Curbing the neutrophil surge: New treatment offers hope for autoimmune diseases

Article References: Curbing the neutrophil surge: New treatment offers hope for autoimmune diseases. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: ANCA-associated vasculitis, glomerulonephritis, neutrophils, autoimmune disease, spatial transcriptomics, Fcγ receptors, kidney injury, University of Osaka, Journal of Experimental Medicine, modified antibodies, neutrophil–epithelial niche, immunology

Antineutrophil cytoplasmic antibody-associated vasculitis, abbreviated as AAV, is a systemic autoimmune disease characterized by necrotizing inflammation of small blood vessels. When it strikes both the lungs and the kidneys, clinicians call it pulmonary-renal syndrome, and it ranks among the most lethal presentations of any autoimmune disease. Patients typically develop rapidly progressive glomerulonephritis, in which the kidney’s filtering units are destroyed within days or weeks, alongside pulmonary infiltrates or diffuse alveolar hemorrhage that can suffocate the patient from within. Without aggressive immunosuppressive treatment, mortality is high and kidney failure is often irreversible.

The patient in this case had been in good health until early 2023, with a medical history notable only for kidney stones. In January 2023, routine laboratory tests revealed persistent leukocytosis, an elevated white blood cell count. Over the following months he developed abdominal pain, muscle and joint aches, low-grade fever, fatigue, and swelling of the lower limbs. Multiple courses of empirical antibiotics were administered without any improvement, a pattern that should raise suspicion of a non-infectious cause. His condition then deteriorated dramatically: urine output fell to oliguria and progressed to complete anuria, accompanied by laboratory evidence of severe systemic inflammation.

On admission to the Department of Nephrology at St. George University Hospital in Plovdiv in May 2023, the man was in poor general condition, with arterial hypertension, peripheral edema, pallor, pulmonary congestion, and clinical signs of fluid overload. Laboratory investigations revealed extreme leukocytosis reaching 41 × 10⁹ per liter, thrombocytosis up to 850 × 10⁹ per liter, markedly elevated inflammatory markers, severe acute kidney injury, electrolyte disturbances, and hypoalbuminemia. Serum creatinine, a key marker of kidney failure, reached 700 µmol/L, while potassium climbed to 6.6 mmol/L, a level that threatens fatal cardiac arrhythmia.

Immunological testing provided the diagnostic turning point. The patient tested positive for proteinase 3-ANCA with a cytoplasmic staining pattern, the immunological signature of this form of vasculitis. Critically, antibodies against the glomerular basement membrane were negative, ruling out Goodpasture’s disease, and microbiological cultures showed no infection. Computed tomography of the chest and abdomen revealed bilateral pulmonary infiltrates, pleural and pericardial effusions, pleural-based pulmonary lesions, and enlarged paraaortic lymph nodes, findings that initially kept both severe infection and malignancy in the differential diagnosis.

A percutaneous kidney biopsy settled the question. Light microscopy showed pauci-immune necrotizing crescentic glomerulonephritis, a pattern in which inflammatory cells form crescent-shaped crescents around the glomeruli while immunofluorescence shows little or no immune complex deposition. This histopathological picture is consistent with PR3-ANCA-associated rapidly progressive glomerulonephritis and, importantly, indicated advanced active disease with an unfavorable prognosis for renal recovery. The extent of crescent formation meant that even with perfect treatment, the kidneys were unlikely to regain function.

Treatment began with the standard induction regimen: high-dose corticosteroids and cyclophosphamide, an alkylating chemotherapy agent that has anchored vasculitis therapy for decades. The patient also received hemodialysis, broad-spectrum antimicrobials including meropenem, vancomycin, and metronidazole, thromboembolic prophylaxis with enoxaparin, and human albumin to correct low blood protein levels. Despite this intensive combination, renal recovery was not achieved, and concerns grew about cumulative cyclophosphamide toxicity, which limits prolonged use particularly in critically ill patients already at high risk of infection.

A multidisciplinary team therefore made the decision to escalate to rituximab, an anti-CD20 monoclonal antibody marketed as MabThera. The pharmaceutical rationale was compelling on several fronts. Rituximab works by selectively depleting CD20-positive B lymphocytes, the cells responsible for producing the ANCA antibodies that drive the inflammatory attack. It has demonstrated efficacy comparable to cyclophosphamide for remission induction, with particular effectiveness in PR3-ANCA-positive disease. Crucially for this dialysis-dependent patient, rituximab is not significantly eliminated through the kidneys and is not effectively removed by hemodialysis, so no dose adjustment was necessary. Before initiating the biologic, the team screened for hepatitis B, hepatitis C, and HIV because of the risk of viral reactivation under immunosuppression.

The outcome demonstrated both the power and the limits of modern therapy. Following rituximab administration, systemic inflammatory activity stabilized and the pulmonary involvement regressed, with no new manifestations outside the kidneys during follow-up. However, renal recovery never occurred, and the patient remained chronically dependent on dialysis, a consequence the authors attribute to the advanced crescentic glomerular injury and the delayed diagnosis. The case underscores a sobering reality: controlling the immune attack cannot always reverse damage already done to organs destroyed before treatment began.

Beyond the individual outcome, the report carries broader lessons for the management of severe vasculitis. Delayed diagnosis and high inflammatory burden are associated with irreversible renal damage and increased mortality, making early recognition of ANCA-associated disease essential when patients present with unexplained kidney failure and lung infiltrates. The authors emphasize that careful pharmaceutical monitoring, including complete blood counts, inflammatory markers, electrolytes, immunoglobulin levels to detect hypogammaglobulinemia, and vigilant surveillance for opportunistic infections, remains essential during biologic immunosuppressive therapy. The successful coordination among nephrologists, clinical pharmacists, pathologists, and intensive care specialists in this case illustrates that multidisciplinary care is not an administrative nicety but a determinant of survival in these complex, rapidly evolving diseases.

Subject of Research: Rituximab therapy for severe PR3-ANCA-associated pulmonary-renal syndrome

Article Title: Rituximab therapy in severe PR3 – ANCA pulmonary–renal syndrome: A clinical and pharmaceutical case report

Article References: Nikolov, D., Nikolov, G., Kitova, L., Kitov, S., Kitova, M.-F., & Mihaylova, A. A. (2026). Rituximab therapy in severe PR3-ANCA pulmonary–renal syndrome: A clinical and pharmaceutical case report. Pharmacia, 73, Article e201634. https://doi.org/10.3897/pharmacia.73.e201634

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DOI: 10.3897/pharmacia.73.e201634

Keywords: rituximab, ANCA-associated vasculitis, pulmonary-renal syndrome, PR3-ANCA, glomerulonephritis, case report, autoimmune disease, kidney failure, hemodialysis, immunosuppression, B-cell depletion, clinical pharmacology

The scientific rationale is compelling. IgA nephropathy follows a multi-hit pathogenic sequence that begins with the production of galactose-deficient IgA1, an abnormally glycosylated antibody. Anti-glycan antibodies bind this molecule to form circulating immune complexes that deposit in the mesangium, the connective tissue scaffolding of the glomerulus. There they trigger local inflammation, predominantly by activating the alternative and lectin complement pathways, with limited evidence for classical pathway involvement. The alternative pathway is considered the dominant amplifier: it is constantly active at low levels in the circulation and can be enhanced by the deposited immune complexes. The lectin pathway, driven by pattern-recognition molecules such as mannan-binding lectin and ficolins that bind directly to the deposits, activates MASP-2 and downstream cleavage of complement components, adding a second engine of glomerular injury.

Both pathways converge at C3, generating the effector molecules C3a and C5a, which recruit inflammatory cells and promote cytokine release, and the membrane attack complex C5b-9, which drives mesangial cell proliferation, oxidative stress and extracellular matrix expansion. Persistent complement activation may also damage the endothelium: several studies have found histological evidence of thrombotic microangiopathy in a subset of patients, particularly severe cases, suggesting an additional injury mechanism that could explain the clinical heterogeneity of the disease. Precisely because complement sits at the center of this pathology, its proteins have become the most closely watched candidate biomarkers in nephrology, especially now that drugs designed to shut down specific complement pathways have reached the clinic.

Among tissue markers, mesangial C4d has emerged as the most extensively studied. Deposits of lectin pathway components are found in roughly 25 to 50 percent of IgA nephropathy biopsies, usually without C1q, supporting lectin pathway involvement. A meta-analysis of 12 studies including 1,251 participants reported an overall prevalence of glomerular C4d deposition of 34 percent. Multiple investigations have shown that C4d-positive patients have greater proteinuria, lower kidney function and adverse Oxford MEST lesions, including mesangial hypercellularity and segmental sclerosis, and deposition has been reported as an independent predictor of progression. Yet C4d has not entered standard risk models, and because lectin pathway activation occurs only in a subset of patients, its relevance to the global population remains unclear.

In the circulation, the factor H-related protein family has attracted particular attention. These proteins, encoded at the complement factor H gene locus, can compete with factor H, the major negative regulator of C3 activation. Plasma FHR-1 is elevated in patients even when kidney function is normal, and the FHR-1 to factor H ratio, proposed as a better measure of the balance between complement control and dysregulation, is significantly raised in patients with progressive disease. FHR-5 tells a different story: it does not track progression but correlates with more severe histological features and a reduced response to immunosuppression, hinting at a role in predicting treatment response. Alternative pathway cleavage products Bb and Ba also carry prognostic weight, with higher Bb linked to vascular and tubular lesions and worse long-term outcomes, while plasma Ba falls after immunosuppression. Low circulating MASP-3, meanwhile, has consistently marked severe, progressive disease.

Conventional serum measures are finding new life as well. In a study of 1,356 Chinese patients, serum C4 correlated with proteinuria, kidney function and the extent of chronic damage, and elevated levels were an independent risk factor for progression. The C3/C4 ratio outperformed either protein alone in predicting poor clinical and pathological features, and in a recent report the addition of serum C3 and C4 improved the predictive performance of both the CKD progression model and the International IgAN Risk Prediction Tool. The IgA/C3 ratio has shown strong diagnostic and prognostic associations in Asian cohorts, but inconsistent results elsewhere mean its generalizability remains unresolved.

Urine offers a non-invasive window onto intrarenal inflammation. Elevated urinary C4d has been associated with greater proteinuria, more severe histopathological injury and increased progression risk, independent of conventional factors, and with poorer response to steroids. Urinary factor H and soluble C5b-9 correlate with proteinuria, interstitial fibrosis and glomerulosclerosis, and a Swedish cohort found that urinary pentraxin 3 and mannan-binding lectin tracked active proliferative lesions while C4c marked chronic fibrosis and faster function decline. A caution remains: most studies lacked proteinuria-matched control groups, so urinary complement may partly reflect nonspecific leakage across a damaged filtration barrier rather than disease-specific activation.

The therapeutic stakes of these measurements are now enormous. The oral factor B inhibitor iptacopan, which suppresses the alternative pathway, reduced proteinuria and slowed kidney function loss in phase 2 and 3 trials, with the final 24-month APPLAUSE-IgAN data showing an annualized total eGFR slope of minus 3.10 versus minus 6.12 ml/min/1.73 m² per year compared with placebo and a kidney-failure endpoint hazard ratio of 0.57. Iptacopan received accelerated FDA approval in 2024 and traditional approval in 2026. The antisense oligonucleotide sefaxersen cut factor B, Bb and urinary Ba while reducing proteinuria by roughly 43 percent in phase 2 and now advances in a phase 3 program. Terminal pathway blockade also works: ravulizumab reduced proteinuria by 30.1 percent versus placebo at week 26, and the siRNA agent cemdisiran achieved a placebo-adjusted 37.4 percent reduction, although it has not progressed to phase 3. By contrast, the MASP-2 inhibitor narsoplimab failed its phase 3 program, a result that highlights the heterogeneity of complement activation and the potential need for biomarker-guided patient selection.

Despite this momentum, the review is candid about the gaps. The KDIGO 2025 guideline states that apart from proteinuria and eGFR there are no validated prognostic serum or urine biomarkers for IgA nephropathy, even while flagging biomarker discovery as a high-priority research recommendation. Most candidate markers have been evaluated in single-center studies with differing assays, non-standardized cut-offs and heterogeneous outcome definitions, yielding moderate and inconsistent performance. Each compartment has inherent limitations: biopsies provide the most direct evidence of complement activation but are invasive and unsuited to repeated monitoring; circulating markers are accessible but may reflect systemic rather than kidney-specific activation; urinary markers are promising but remain largely unvalidated. Complement activation also differs across ethnic populations and may shift over the course of disease.

The authors argue that the field’s priority should now shift from proving that complement matters to identifying which patients benefit most from which inhibitor, guided by pathway-specific biomarkers. The principle they invoke is straightforward: right pathway, right drug, right patient, right time. Biomarker-driven stratification could match pathway activity to targeted therapy, minimize unnecessary immunosuppression and reduce adverse effects, and may eventually reveal whether patients with complement-mediated thrombotic microangiopathy, a phenotype so far studied only in case reports, derive special benefit from complement inhibition. Large, multiethnic, longitudinal studies will be needed before complement biomarkers can move from research tool to routine clinical practice, but with effective complement drugs already approved, the incentive to validate them has never been greater.

Subject of Research: Complement biomarkers for diagnosis, prognosis and complement-targeted therapy in IgA nephropathy

Article Title: Complement biomarkers in IgA nephropathy: current insights and clinical relevance

Article References: Balmukhanova, A., Chan, C. E., & Barratt, J. (2026). Complement biomarkers in IgA nephropathy: current insights and clinical relevance. Frontiers in Nephrology, 6, Article 1918450. https://doi.org/10.3389/fneph.2026.1918450

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DOI: 10.3389/fneph.2026.1918450

Keywords: IgA nephropathy, complement system, biomarkers, C4d, alternative pathway, lectin pathway, iptacopan, kidney disease, glomerulonephritis, precision medicine, proteinuria, nephrology

ANCA-associated vasculitis, or AAV, is a family of necrotizing small-vessel diseases driven by pathogenic antineutrophil cytoplasmic antibodies. It encompasses microscopic polyangiitis, granulomatosis with polyangiitis, and eosinophilic granulomatosis with polyangiitis. Classically, patients present with striking systemic features—rapidly rising creatinine, pulmonary hemorrhage, palpable purpura, peripheral neuropathy—that trigger an immunological workup and serological testing. Bronchiectasis, by contrast, is rarely considered an inaugural manifestation. When it appears in AAV, it is usually interpreted as structural fallout from established vasculitic inflammation rather than a warning shot, a framing that can postpone ANCA testing until organ damage declares itself elsewhere.

The patient at the center of the report arrived in 2018 with a chronic productive cough and a history of intermittent asthma. High-resolution computed tomography revealed focal bronchiectasis confined to the right middle lobe. Her physicians did what good diagnosticians do: they systematically excluded the usual suspects. Serial sputum cultures and bronchoalveolar lavage were negative for bacterial, mycobacterial, and fungal pathogens. Non-tuberculous mycobacterial infection, cystic fibrosis, primary immunodeficiency, allergic bronchopulmonary aspergillosis, and eosinophilic granulomatosis with polyangiitis were all ruled out. Spirometry was normal. Empiric corticosteroids and macrolides were prescribed for presumed non-infective airway inflammation, and her symptoms improved—but never resolved.

Over the following six years, repeat imaging charted a slow, ominous march. The focal right middle lobe disease progressed to multifocal bilateral bronchiectasis, accompanied by tree-in-bud nodularity and mucus plugging, with new parenchymal nodules appearing along the way. Her antinuclear antibody test was negative. Critically, ANCA serology was never obtained, and the diagnosis remained bronchiectasis of undetermined etiology for seven years. The authors of the report are careful not to overclaim causality, but they highlight a stark, narrower fact: seven years elapsed during which an inexpensive blood test that would have reframed the entire diagnosis was never sent.

Then, in 2025, the systemic disease erupted. The woman developed palpable purpura across both lower extremities, hemoptysis, and hematuria. Imaging showed new multifocal bilateral consolidations superimposed on the established bronchiectasis, though without the ground-glass pattern of diffuse alveolar hemorrhage; her hemoglobin and oxygen saturation remained stable and the hemoptysis resolved spontaneously. Her kidneys told a more urgent story. Serum creatinine had surged from 0.46 mg/dL six weeks earlier to 2.09 mg/dL—an estimated glomerular filtration rate collapsing from 100 to 24 mL/min/1.73 m²—and reached a nadir of 2.19 mg/dL on hospital day three, all while urine output remained preserved.

The serology finally caught up with the disease. Indirect immunofluorescence showed a perinuclear pattern, and antigen-specific ELISA confirmed myeloperoxidase-ANCA, or MPO-ANCA, at 250.2 U/mL against a reference value below 1.0, with proteinase 3-ANCA negative. Urinalysis revealed proteinuria with dysmorphic erythrocytes. A renal biopsy sampling fourteen glomeruli showed pauci-immune crescentic glomerulonephritis with a cellular crescent in one glomerulus, no immune deposits, and more than half of the glomeruli intact—Berden focal class, the histological category carrying the most favorable prognosis. Anti-glomerular basement membrane and anti-double-stranded DNA antibodies were negative, and complement was normal. Together, the findings established microscopic polyangiitis.

Treatment followed current guidelines: three days of intravenous methylprednisolone at 500 mg daily, an oral prednisone taper, and rituximab 1 gram repeated after two weeks and then every six months as maintenance, with Pneumocystis prophylaxis. The response was dramatic on the inflammatory front. Within two months her eGFR peaked at 74, stabilizing at 60 at fifteen months—stage 3a chronic kidney disease, a plateau the authors attribute to residual nephron loss after inflammatory suppression. At five months, high-resolution CT showed near-complete resolution of the consolidations, while the underlying bronchiectasis persisted, exactly as expected for fixed structural airway damage. MPO-ANCA fell from 250.2 to 5.2 U/mL by twelve months with documented B-cell depletion, and she remains asymptomatic at fifteen months, her cough finally resolved.

The literature review embedded in the report gives the case its wider significance. A 2024 systematic review and meta-analysis of 24 studies found a pooled bronchiectasis prevalence of 19 percent in AAV—higher with MPO-ANCA than PR3-ANCA, at 28 percent versus 13 percent—and noted that bronchiectasis may precede, coincide with, or follow the vasculitis. One retrospective cohort of 58 AAV patients found bronchiectasis in 37.9 percent, all MPO-ANCA positive, independently associated with MPO specificity, female sex, and age at diagnosis. Most striking is a multicentre cohort of 61 patients with AAV and bronchiectasis: in 25 of them, bronchiectasis preceded the vasculitis by a median of 16 years, and this bronchiectasis-first group had more microscopic polyangiitis, more MPO-ANCA, and shorter survival. The present patient—female, MPO-positive, with airway disease antedating systemic vasculitis by seven years—fits that phenotype precisely.

Yet the authors resist a simple causal narrative, and the evidence supports their caution. Where bronchiectasis was universally MPO-associated, affected patients actually had less frequent renal involvement than those without it, and bronchiectasis in AAV generally does not respond to immunosuppression—consistent with this patient, whose consolidations melted away while the structural airway disease remained. Whether earlier serology would have changed her outcome is genuinely uncertain. The real gap, they argue, lies in the current diagnostic algorithms. The 2025 European Respiratory Society guideline strongly recommends standardized testing for the underlying cause of bronchiectasis, but ANCA appears only within an etiological algorithm gated behind systemic features—coexisting autoimmune disease, hemoptysis, or signs of vasculitis—and the guideline explicitly states these components are not separate recommendations. A 2025 observational study screening 468 bronchiectasis patients found ANCA positivity in just 3.8 percent and concluded screening should remain individualized. The 2026 American College of Chest Physicians guideline addresses management only. This patient had none of the trigger features before 2025: her gap sits outside current algorithms—culture-negative, radiographically progressive, incompletely corticosteroid-responsive disease without systemic features.

One diagnostic alternative deserved careful exclusion. The combination of MPO-ANCA positivity, long-standing airway disease, and a history of asthma raises eosinophilic granulomatosis with polyangiitis as the leading rival. Applying the 2022 ACR/EULAR classification criteria is instructive: her cumulative score was just 2 points—3 for obstructive airway disease, credited on her asthma history despite normal spirometry, minus 1 for hematuria—far below the 6 required, because the most heavily weighted item, a maximum eosinophil count of at least 1 × 10⁹ per liter, was never met. Eosinophils were 0 percent at presentation and had never been elevated; total IgE, measured in 2024, was 114 kU/L without the marked elevation characteristic of EGPA. Pauci-immune crescentic glomerulonephritis with markedly elevated MPO-ANCA and no tissue or blood eosinophilia settles the question in favor of microscopic polyangiitis. The case also carries a technical lesson in serology: the discordance between her falling MPO-ANCA titers and persistent weak immunofluorescence positivity is compatible with non-MPO perinuclear antibodies during B-cell depletion, reinforcing guidance against basing treatment decisions on titers alone. Limitations remain—alveolar hemorrhage was never definitively confirmed, and the absence of ANCA testing during the airway phase means the timing of seroconversion is unknown. What endures is the clinical message: in a patient with progressive, culture-negative bronchiectasis that resists the usual treatments, the vasculitis may already be knocking, years before the door gives way.

Subject of Research: Bronchiectasis as an early sentinel manifestation of ANCA-associated vasculitis

Article Title: Bronchiectasis as the Sentinel Manifestation of ANCA‐Associated Vasculitis: A Case Report and Literature Review

Article References: Kim, A., Vartany, C., Hegde, S., Lau, K., Tatosyan, L., & Liang, B. (2026). Bronchiectasis as the Sentinel Manifestation of ANCA ‐Associated Vasculitis: A Case Report and Literature Review. Respirology Case Reports, 14(10), Article e70777. https://doi.org/10.1002/rcr2.70777

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DOI: 10.1002/rcr2.70777

Keywords: bronchiectasis, ANCA-associated vasculitis, microscopic polyangiitis, MPO-ANCA, case report, glomerulonephritis, rituximab, high-resolution CT, EGPA, clinical guidelines, autoimmune screening, respiratory medicine

COPA syndrome is caused by mutations in the COPA gene, which encodes the alpha subunit of the coatomer protein complex, a cellular machine responsible for shuttling proteins between the endoplasmic reticulum and the Golgi apparatus. When this trafficking system breaks down, proteins accumulate abnormally within cells, triggering cellular stress and activating the type I interferon pathway, a central alarm system of innate immunity. The result is profound immune dysregulation characterized by the production of autoantibodies and chronic inflammation that primarily targets the lungs, kidneys and joints. The condition is usually inherited in an autosomal dominant pattern, although sporadic cases without any family history occur, and the classic clinical triad comprises interstitial lung disease or diffuse alveolar hemorrhage, arthritis and kidney disease.

The patient at the center of the report first fell ill at the age of 27, when he developed flu-like symptoms, coughing up blood and acute respiratory failure severe enough to require orotracheal intubation and eighteen days of mechanical ventilation. Chest computed tomography at that time revealed diffuse alveolar damage and a nonspecific interstitial pneumonia pattern. Within the same year he began showing signs of renal dysfunction, and a year later he suffered a second episode of acute respiratory failure. Given the striking combination of lung bleeding and kidney injury, his physicians initially suspected a pulmonary–renal syndrome such as ANCA-associated vasculitis or Goodpasture syndrome, and in 2008 he was started on an intensive course of twelve cycles of the immunosuppressant cyclophosphamide.

That treatment achieved partial stabilization, but it could not halt the underlying disease. Serial chest CT scans over the following years documented progressive fibrotic damage to the lungs, including upper lobe–predominant honeycombing, increasing reticulation, traction bronchiectasis and persistent ground-glass opacities. By 2022, high-resolution imaging showed established fibrotic remodeling alongside findings suggesting active inflammatory lung injury, a coexistence of chronic scarring and recurrent acute damage that is characteristic of the heterogeneous pulmonary manifestations of COPA syndrome. A transbronchial biopsy yielded inadequate tissue, so the surgical team proceeded to an open lung biopsy. The histopathology proved remarkably rich: prominent lymphoid follicles consistent with follicular bronchiolitis, a non-fibrotic nonspecific interstitial pneumonia pattern with marked interstitial edema, patches of organizing pneumonia containing intra-alveolar fibrin in an acute fibrinous and organizing pneumonia pattern, fibrin thrombi within airspaces, and evidence of both recent and remote alveolar hemorrhage in the form of hemosiderin-laden macrophages.

The kidneys told a parallel story. A renal biopsy performed in November 2008 demonstrated focal proliferative and necrotizing glomerulonephritis with early crescent formation in six of nine glomeruli examined, confirming active immune-mediated renal injury. Immunofluorescence showed no linear deposition of immunoglobulin along the glomerular basement membrane, which definitively excluded Goodpasture syndrome. Serologic testing during reevaluation between 2021 and 2022 revealed a positive antinuclear antibody test at a titer of 1:320 in a homogeneous pattern and a positive p-ANCA at 1:80, but antibodies directed against myeloperoxidase, proteinase 3, double-stranded DNA, Smith, ribonucleoprotein, Ro/SSA and La/SSB were all negative. Kidney function was impaired, with a creatinine clearance of 60 mL per minute and 24-hour proteinuria of 907.5 mg. The atypical ANCA positivity, the authors note, reflects the immune dysregulation inherent to COPA syndrome rather than primary ANCA-associated vasculitis, a distinction with major consequences for classification and treatment.

The definitive answer arrived only in January 2024, when next-generation sequencing identified a heterozygous COPA variant, NM_004371.4:c.698G>A (p.Arg233His), classified as likely pathogenic under American College of Medical Genetics criteria. This variant had been reported previously in individuals with COPA syndrome and is associated with pulmonary and autoimmune manifestations, and its identification finally unified the patient’s pulmonary hemorrhage, crescentic glomerulonephritis and arthralgia under a single genetic diagnosis. Notably, the patient had denied any family history of autoimmune, interstitial lung or renal disease, and genetic testing of relatives was unavailable, underscoring how sporadic presentations can escape suspicion for years. Pulmonary function testing in 2022 revealed a mixed moderate obstructive and restrictive ventilatory defect, with a forced vital capacity of 53 percent predicted, a forced expiratory volume in one second of 44 percent predicted and a markedly reduced diffusing capacity for carbon monoxide at 42 percent predicted. A six-minute walk test showed oxygen saturation falling from 96 percent to 85 percent after only 285 meters.

Once the diagnosis was confirmed, the nephrology team initiated maintenance immunosuppression with methotrexate 10 mg weekly and prednisone 10 mg daily, and the patient remained clinically stable and asymptomatic for roughly a year. The course then deteriorated for reasons that were tragically behavioral as much as biological. The patient self-adjusted his medications, discontinued methotrexate without medical advice because he attributed his symptoms to a viral infection, and stopped attending scheduled follow-up visits. After approximately a year without immunosuppressive therapy, he returned with worsening renal function and significant proteinuria while his lung disease remained stable. Suspecting immune-mediated renal relapse, clinicians began pulse cyclophosphamide at 1 g daily for three consecutive days together with pulse methylprednisolone at the same dose and schedule, with no documented neutropenia during treatment.

Shortly after that single cycle, the patient developed acute diverticulitis complicated by sepsis from a perforated diverticulum, an event for which he had no prior history of diverticular disease. He underwent an emergency Hartmann’s procedure with end colostomy for surgical source control, but despite emergency abdominal surgery and prolonged broad-spectrum antibiotics, he progressed to septic shock and multiorgan failure and died. The case authors emphasize that severe infection during potent immunosuppression is among the principal causes of mortality reported in COPA syndrome, alongside progressive respiratory failure and end-stage kidney disease, and that patients receiving cyclophosphamide and similar agents require particularly vigilant multidisciplinary monitoring.

Beyond its clinical drama, the report carries broader lessons for the field. Because COPA syndrome is rare and phenotypically variable, diagnostic delay is common, especially when adult presentations overlap with far more prevalent autoimmune and interstitial lung diseases. The authors argue that the diagnosis should be suspected in patients with diffuse alveolar hemorrhage, unexplained pulmonary–renal syndromes, follicular bronchiolitis or interstitial lung disease beginning in childhood or early adulthood, particularly when autoantibodies are positive without a definitive connective tissue disease diagnosis. Genetic testing, they contend, should be pursued whenever diagnostic uncertainty persists despite multidisciplinary evaluation. On the therapeutic horizon, Janus kinase inhibitors such as baricitinib and ruxolitinib, which target the type I interferon pathway at the root of the disease, have shown promise in case reports and small studies and may prove especially valuable for severe or refractory disease. The authors call for multicenter studies and international registries to standardize treatment strategies and define the natural history of the condition, and they conclude that early recognition, sustained treatment adherence and careful monitoring during immunosuppressive therapy are essential to prevent relapse and fatal complications in this rare but devastating disorder.

Subject of Research: COPA syndrome, a rare autosomal dominant genetic autoimmune disorder affecting the lungs, kidneys and joints

Article Title: A Rare Case of COPA Syndrome: Multisystem Relapse and Fatal Septic Complication

Article References: Castro Velasco Fernandes, F., Torres, P. P. T. E. S., de Paula Silveira‐Lacerda, E., Rabahi, M., Velasco Magalhaes Fernandes, L., Lopes, L. R., Moreira, M. A. R., & Rabahi, M. F. (2026). A Rare Case of COPA Syndrome: Multisystem Relapse and Fatal Septic Complication. Respirology Case Reports, 14(9), Article e70742. https://doi.org/10.1002/rcr2.70742

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DOI: 10.1002/rcr2.70742

Keywords: COPA syndrome, genetic autoimmune disease, interstitial lung disease, diffuse alveolar hemorrhage, glomerulonephritis, COPA gene mutation, immunosuppression, sepsis, next-generation sequencing, type I interferon, follicular bronchiolitis, pulmonary-renal syndrome