ANCA-associated vasculitis Medical Services in China

ANCA-associated vasculitis (AAV) is a group of rare, systemic autoimmune disorders characterized by inflammation and necrosis of small- to medium-sized blood vessels, primarily driven by autoantibodies against neutrophil cytoplasmic antigens (ANCAs). The three main clinical entities under this umbrella are granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). These diseases predominantly affect the kidneys, lungs, upper airways, skin, nerves, and joints. Pathogenesis centers on dysregulated neutrophil activation: ANCAs—most commonly targeting proteinase 3 (PR3-ANCA in GPA) or myeloperoxidase (MPO-ANCA in MPA and EGPA)—bind to primed neutrophils, triggering uncontrolled degranulation, reactive oxygen species release, and endothelial injury. This cascade leads to pauci-immune necrotizing glomerulonephritis (a hallmark renal lesion), pulmonary capillaritis, and granulomatous inflammation in GPA. Genetic susceptibility (e.g., HLA-DQ variants, PRTN3 polymorphisms), environmental triggers (e.g., silica exposure, chronic nasal Staphylococcus aureus colonization, certain drugs like hydralazine or propylthiouracil), and epigenetic dysregulation contribute to disease onset. Epidemiologically, AAV affects approximately 10–20 new cases per million people annually worldwide, with prevalence estimated at 50–250 per million. Incidence rises sharply after age 50, peaking in the seventh decade; males and females are equally affected overall, though GPA shows slight male predominance. In China, AAV is increasingly recognized but likely underdiagnosed due to nonspecific early symptoms and limited ANCA testing access outside major centers. Key risk factors include older age, chronic sinusitis or asthma (especially in EGPA), occupational silica exposure, smoking, and certain infections. Renal involvement—present in up to 80% of GPA and MPA cases—often manifests as rapidly progressive glomerulonephritis (RPGN), leading to acute kidney injury and, if untreated, end-stage kidney disease requiring dialysis or transplantation. Beyond renal morbidity, patients frequently experience debilitating fatigue, arthralgias, neuropathy, pulmonary hemorrhage, and persistent upper respiratory tract damage. Quality of life is profoundly impacted: over 60% report moderate-to-severe impairment in physical functioning, role limitations, and mental health; depression and anxiety rates exceed population norms by 3–4 fold. Chronic immunosuppression increases infection risk and long-term cardiovascular morbidity, while treatment-related side effects—including osteoporosis, diabetes, cataracts, and malignancy—further erode well-being. Early diagnosis via ANCA serology (ELISA + IIF), renal biopsy (showing pauci-immune crescentic GN), and imaging (e.g., CT chest/sinus) is critical. Delayed recognition remains common, contributing to irreversible organ damage and higher mortality—5-year survival ranges from 70% to 85%, heavily dependent on timely intervention and sustained remission maintenance.

ANCA-associated vasculitis (AAV) is a group of systemic autoimmune disorders characterized by necrotizing inflammation of small- to medium-sized blood vessels, strongly associated with antineutrophil cytoplasmic antibodies (ANCA). The three primary clinical phenotypes—granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA)—frequently involve the kidneys, manifesting as pauci-immune crescentic glomerulonephritis. As such, nephrology departments play a central role in diagnosis, risk stratification, and longitudinal management. Treatment is stratified by disease severity (limited vs. severe/organ-threatening), renal function at presentation, and histopathological findings on kidney biopsy.

Conservative treatment forms the essential foundation of AAV management and must be initiated concurrently with immunosuppression. This includes strict blood pressure control targeting <130/80 mmHg using renin-angiotensin-aldosterone system inhibitors (e.g., ACE inhibitors or ARBs), which confer dual benefits of antiproteinuric and renoprotective effects. Fluid and electrolyte balance must be meticulously monitored, especially in patients with acute kidney injury (AKI) or rapidly progressive glomerulonephritis (RPGN); diuretics may be required for volume overload, while sodium restriction (<2 g/day) and potassium monitoring are critical in advanced chronic kidney disease (CKD). Nutritional support is vital: a low-sodium, moderate-protein (0.8–1.0 g/kg/day) diet helps mitigate glomerular hyperfiltration and uremic complications without compromising immune competence. Smoking cessation is non-negotiable, given its strong association with disease relapse and reduced treatment response. Vaccination status must be reviewed and updated—particularly pneumococcal, influenza, hepatitis B, and SARS-CoV-2 vaccines—prior to initiating immunosuppression, as live vaccines are contraindicated during active therapy.

Pharmacotherapy remains the cornerstone of AAV treatment and follows a biphasic strategy: induction and maintenance. For severe disease (e.g., serum creatinine >300 µmol/L, >50% crescents on biopsy, or pulmonary-renal syndrome), induction therapy consists of high-dose glucocorticoids (prednisone 1 mg/kg/day tapered over 3–6 months) combined with either cyclophosphamide (oral 2 mg/kg/day or IV pulse regimens) or rituximab (375 mg/m² weekly ×4 or 1000 mg ×2 doses two weeks apart). Rituximab is now preferred for both GPA and MPA in most guidelines—including KDIGO 2021—due to superior safety profile, particularly regarding gonadal toxicity and malignancy risk. For EGPA with predominant asthma/eosinophilia and no major organ involvement, mepolizumab or benralizumab (anti-IL-5 biologics) may be considered adjunctively, though evidence remains limited. Maintenance therapy begins after remission is achieved (typically within 3–6 months) and continues for ≥24–48 months. Azathioprine (2 mg/kg/day) or mycophenolate mofetil (1–1.5 g twice daily) are standard options; rituximab (500–1000 mg every 6 months) is increasingly used for sustained remission, especially in relapsing disease. Plasma exchange (PLEX) is indicated for severe RPGN (serum creatinine >500 µmol/L or dialysis dependence) or diffuse alveolar hemorrhage, with protocols typically involving 7 sessions over 14 days. Adjunctive therapies include prophylaxis against Pneumocystis jirovecii pneumonia (e.g., trimethoprim-sulfamethoxazole), calcium/vitamin D supplementation, and bisphosphonates for steroid-induced osteoporosis.

Surgical intervention is rarely indicated in AAV but may be necessary in specific complications. End-stage kidney disease (ESKD) resulting from irreversible glomerulosclerosis and interstitial fibrosis requires renal replacement therapy—either hemodialysis, peritoneal dialysis, or kidney transplantation. Transplantation is feasible once disease has been quiescent for ≥12–24 months and ANCA titers are persistently negative; recurrence rates post-transplant are low (<5% at 5 years) but necessitate vigilant monitoring. Sinus surgery may be performed in GPA patients with refractory sinonasal granulomatous disease unresponsive to medical therapy, improving drainage and reducing infection burden. Tracheal stenosis—a late complication of GPA—may require endoscopic dilation or airway stenting, and in severe cases, surgical resection with reconstruction. Pulmonary nodules or cavitary lesions that fail to regress or demonstrate atypical growth patterns warrant biopsy to exclude malignancy or infection, though surgical resection is seldom first-line.

China offers distinct advantages in the multidisciplinary management of AAV. First, integrated nephrology-rheumatology-immunology centers—such as those at Peking University First Hospital and Shanghai Renji Hospital—employ standardized, protocol-driven care pathways aligned with international guidelines yet adapted to regional epidemiology and pharmacogenomic profiles (e.g., optimized cyclophosphamide dosing based on CYP2B6 polymorphisms). Second, China’s national rare disease registry and centralized biobanks facilitate rapid access to real-world data, enabling timely identification of treatment responders and early detection of relapse via serial ANCA monitoring and urinary biomarkers (e.g., CD163+ monocytes, NGAL). Third, cost-effective biosimilar rituximab and domestically manufactured mycophenolate formulations significantly improve treatment accessibility, particularly in tier-2 and tier-3 cities. Fourth, traditional Chinese medicine (TCM) adjuncts—such as Huangqi (Astragalus membranaceus) and Danshen (Salvia miltiorrhiza)—are rigorously studied in randomized controlled trials for their anti-fibrotic and endothelial-stabilizing properties; several TCM formulas have demonstrated additive benefit in reducing proteinuria and delaying CKD progression when co-administered with standard immunosuppression, under strict pharmacovigilance oversight.

Recovery and long-term follow-up demand structured patient engagement. Patients should undergo quarterly nephrology visits for assessment of eGFR, urinalysis, ANCA titers, and complement levels; annual chest CT and ENT evaluation are recommended for GPA. Home blood pressure and weight monitoring empower early recognition of fluid retention or hypertension flare. Physical rehabilitation—including graded aerobic exercise and resistance training—is encouraged to counteract steroid-induced myopathy and improve cardiovascular fitness. Psychosocial support is integral: depression and anxiety affect >30% of AAV survivors, and dedicated counseling services are embedded in major Chinese nephrology centers. Finally, fertility preservation counseling should be offered prior to cyclophosphamide initiation, and pregnancy planning must occur only after ≥12 months of stable remission and normalized renal function. With contemporary protocols, 5-year patient survival exceeds 85%, and renal survival surpasses 75% in those presenting with preserved baseline eGFR—underscoring the importance of early diagnosis, precision immunosuppression, and lifelong nephrology stewardship.