Eosinophilic granulomatosis with polyangiitis, abbreviated EGPA and formerly called Churg-Strauss syndrome, is a rare form of vasculitis, meaning it involves inflammation of blood vessels. It belongs to a family of conditions known as antineutrophil cytoplasmic antibody, or ANCA, associated vasculitides, although not every patient produces these antibodies. The disease is characterised by an overabundance of eosinophils, a type of white blood cell normally deployed against parasites and involved in allergic reactions. When these cells accumulate and activate inappropriately, they can wreak havoc on organs throughout the body, including the lungs, skin, heart, and, critically, the peripheral nerves, the delicate wiring that carries signals between the spinal cord and the rest of the body.

Peripheral neuropathy, the medical term for damage to these nerves, is among the most feared manifestations of EGPA. Patients may experience numbness, tingling, weakness, or excruciating pain, typically beginning in the feet and hands. In the most severe cases, the damage follows a pattern known as mononeuritis multiplex, in which multiple individual nerves fail in unpredictable succession, leaving patches of the body paralysed or insensate. Despite decades of clinical observation, the underlying mechanisms that drive nerve injury in EGPA remain poorly understood, and clinicians have lacked dependable laboratory markers to identify which patients are developing or will develop this complication.

The new study, published in the Journal of Neurology, set out to address this gap. Researchers led by Yuichi Masuda and Shogo Matsuda of Osaka Medical and Pharmaceutical University, together with collaborators at Kyoto University, Osaka Metropolitan University, Yodogawa Christian Hospital, Tenri Hospital, and Kurashiki Sweet Hospital, assembled data from the REVEAL cohort, a multicentre database covering patients diagnosed across Japan. They enrolled individuals newly diagnosed with EGPA between 2006 and 2024, applying the 2022 classification criteria jointly developed by the American College of Rheumatology and the European Alliance of Associations for Rheumatology, the current international standard for identifying the disease.

From an initial pool of 159 patients in the REVEAL cohort, the investigators focused on 107 patients who were newly diagnosed and had not yet received any treatment, a design choice that eliminates the confounding effects of prior immunosuppressive therapy on laboratory values and clinical findings. The results were striking. Peripheral neuropathy was present in 93 of the 107 patients, an extraordinary 86.9 percent, underscoring just how central nerve involvement is to the clinical picture of EGPA in this Japanese population. Meanwhile, 45 patients, or 42.1 percent, tested positive for myeloperoxidase ANCA, one of the two major antibody types associated with this disease family.

When the researchers compared patients with neuropathy against those without, several laboratory parameters stood out. Patients with peripheral nerve involvement had significantly higher levels of white blood cells, eosinophils, serum immunoglobulin G, and serum immunoglobulin G4 at the time of diagnosis. Among these candidates, IgG4 emerged as the most useful clinical indicator for detecting neuropathy in EGPA patients. This finding carries particular biological interest. IgG4 is an unusual antibody subclass, associated with immune tolerance rather than aggressive inflammation, and it has previously been implicated in IgG4-related disease, a distinct fibroinflammatory condition. Earlier work had already documented IgG4 immune responses in Churg-Strauss syndrome, and pathological studies have found IgG4-related features in inflammatory neuropathies, making the new cohort data a compelling piece of a growing puzzle.

The study also examined what happens to patients over time, and here the news was mixed. Using Kaplan-Meier survival analysis, a standard statistical technique for tracking events over follow-up periods, the team calculated that the five-year relapse rate of peripheral neuropathy among EGPA patients who had experienced it was 18.6 percent. In other words, nearly one in five patients whose nerve disease had initially been brought under control saw it return within five years. Relapse in vasculitis is a persistent clinical challenge, and identifying which patients are at risk has been an ongoing goal of international research efforts, including the European Vasculitis Study Group trials, which previously documented the burden of peripheral neuropathy in ANCA-associated vasculitis more broadly.

Perhaps the most actionable finding concerned treatment. The researchers found that the administration rate of intravenous cyclophosphamide, a potent immunosuppressive drug long used in severe forms of vasculitis, was significantly lower among patients whose neuropathy relapsed than among those who remained in remission. While the observational design of the study means it cannot definitively prove that cyclophosphamide prevents relapse, the association suggests that more aggressive induction therapy at the outset may protect the nerves over the long term. This aligns with contemporary European guidelines for managing ANCA-associated vasculitis, which recommend cyclophosphamide or rituximab for organ-threatening disease, and with recent trials exploring glucocorticoids combined with cyclophosphamide in EGPA patients with poor-prognosis factors.

The implications for clinical practice are potentially significant. A readily available serum marker like IgG4 could help clinicians stratify newly diagnosed EGPA patients, flagging those who need close neurological monitoring, nerve conduction studies, or early escalation of immunosuppression. It could also complement existing prognostic tools, such as the revised five-factor score used to assess mortality risk in systemic necrotizing vasculitides, and disease activity measures like the Birmingham Vasculitis Activity Score version 3.0, which the current study used to characterise patients at baseline. For a disease in which diagnosis is often delayed for years while patients are treated for asthma alone, any additional diagnostic lever is welcome.

Caution is nonetheless warranted. The study involved 107 patients from a single country, and the authors themselves note that the aetiology of peripheral neuropathy in EGPA remains unclear. Whether IgG4 is merely a correlate of the eosinophilic, ANCA-negative disease subset that tends toward neuropathy, or plays a direct role in nerve injury, awaits further mechanistic work. The finding that lower cyclophosphamide use was associated with relapse could reflect confounding by disease severity, since physicians may reserve the drug for the sickest patients. Still, with newer targeted therapies such as the anti-interleukin-5 agent mepolizumab showing promise for EGPA-related neuropathy in recent reports, the landscape of treatment options is expanding. The REVEAL cohort study adds an important piece of evidence to this evolving picture, offering clinicians a potential biomarker and a hint that early, intensive immunosuppression may keep patients’ nerves, and their independence, intact for longer.

Subject of Research: Peripheral neuropathy in eosinophilic granulomatosis with polyangiitis

Article Title: Clinical features and prognosis of EGPA-associated peripheral neuropathy: a multicentre REVEAL cohort study

Article References: Masuda, Y., Matsuda, S., Okazaki, A., Tsuge, R., Manabe, A., Taniguchi, T., Hiwa, R., Hatta, M., Shiomi, M., Watanabe, R., Suwa, N., Fujiki, Y., Miyake, H., Yamamoto, W., Hashimoto, M., Takeuchi, T., & Kotani, T. (2026). Clinical features and prognosis of EGPA-associated peripheral neuropathy: a multicentre REVEAL cohort study. Journal of Neurology, 273(10), Article 641. https://doi.org/10.1007/s00415-026-14196-z

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14196-z

Keywords: EGPA, peripheral neuropathy, vasculitis, IgG4, ANCA, cyclophosphamide, eosinophils, autoimmune disease, REVEAL cohort, biomarker, relapse, Journal of Neurology

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

Image Credits: AI Generated

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