Eosinophilic Granulomatosis with Polyangiitis
A rare autoimmune disease causing blood vessel inflammation, characteristically presenting with adult-onset severe asthma, high eosinophil counts, and nerve or heart damage.
Emergency Management: Rapidly progressive glomerulonephritis or acute heart failure due to myocarditis requires emergent ICU admission, IV pulse steroids, and urgent initiation of Cyclophosphamide.
Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare, systemic, anti-neutrophil cytoplasmic antibody (ANCA)-associated small-to-medium vessel vasculitis. It is characterized by severe asthma, tissue and blood eosinophilia, and necrotizing granulomatous inflammation.
Detailed Overview
EGPA typically evolves in three sequential clinical phases: an allergic/prodromal phase (asthma, allergic rhinitis), an eosinophilic phase (tissue infiltration by eosinophils, notably in the lungs and GI tract), and a vasculitic phase (systemic necrotizing vasculitis affecting nerves, heart, and skin). Cardiac involvement is the leading cause of mortality.
Epidemiology & Demographics
Very rare, with an incidence of 1-3 cases per million per year. Mean age of onset is around 40-50 years. Affects males and females equally.
Etiological Mechanism
The exact cause is unknown. It is considered an autoimmune disorder triggered by environmental agents in genetically susceptible individuals, leading to a Th2-mediated immune dysregulation.
Primary Causes
Dysregulation of the immune system leading to Th2 predominance, hypersecretion of IL-5, massive eosinophil proliferation, and ANCA production (in ~40% of cases) leading to endothelial damage.
EGPA is driven by a Th2-polarized immune response resulting in excessive production of Interleukin-5 (IL-5). IL-5 promotes profound bone marrow production, activation, and survival of eosinophils. These eosinophils infiltrate tissues, degranulating and releasing toxic proteins (e.g., Major Basic Protein) that cause direct tissue damage (especially in the myocardium and GI tract). Concurrently, about 40% of patients develop MPO-ANCA (Myeloperoxidase-ANCA). ANCA activates neutrophils to adhere to endothelium and release reactive oxygen species and proteases, causing necrotizing vasculitis, which leads to ischemia in peripheral nerves, skin, and kidneys.
Diagnostic Criteria & Guidelines
American College of Rheumatology (ACR) criteria require 4 of 6: 1) Asthma, 2) Eosinophilia > 10% on diff, 3) Mononeuropathy or polyneuropathy, 4) Migratory/transient pulmonary opacities, 5) Paranasal sinus abnormality, 6) Biopsy showing extravascular eosinophils.
For active, non-severe disease: High-dose systemic corticosteroids (Prednisone 1 mg/kg/day) tapering over months. For severe/life-threatening disease (cardiac, renal, CNS involvement, or severe neuropathy) defined by a Five-Factor Score (FFS) > 0: Pulse IV Methylprednisolone (1000 mg daily for 3 days) PLUS Cyclophosphamide (IV pulses 0.6 g/m2 every 2-3 weeks, or 2 mg/kg/day PO) or Rituximab (375 mg/m2 weekly x 4).
Second-Line & Adjunctive Therapy
For remission maintenance or refractory/relapsing non-severe disease: Mepolizumab (anti-IL-5 monoclonal antibody, 300 mg SQ every 4 weeks) is highly effective at inducing remission, reducing exacerbations, and sparing corticosteroid use. Azathioprine or Methotrexate are used for maintenance therapy following cyclophosphamide induction.
Surgical & Procedural Management
Endoscopic sinus surgery for severe, obstructive nasal polyposis. Rarely, bowel resection if vasculitic ischemia causes bowel perforation.
Patient Counseling & Advice
Inform the patient that while the disease is chronic and requires long-term immunosuppression, remission is achievable. Emphasize the importance of reporting any new nerve pain/weakness or chest pain immediately.
Follow-Up & Monitoring Schedule
Monitor clinical symptoms, absolute eosinophil count, CRP, renal function (creatinine, urinalysis for red cell casts), and ANCA titers closely. Serial echocardiography to monitor cardiac status.
Preventive Strategies
No known prevention. Early recognition in asthmatic patients developing unusually high eosinophil counts or nerve pain prevents irreversible end-organ damage.
Without treatment, 5-year survival is <25%. With modern immunosuppression, 5-year survival exceeds 80-90%, but relapses are common and treatment-related morbidity (steroid toxicity, infections) is high.