Eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as Churg-Strauss syndrome, is a rare form of vasculitis affecting small to medium-sized blood vessels. It primarily impacts individuals with a history of asthma or allergic conditions and is characterized by elevated eosinophil levels, systemic inflammation, and multi-organ involvement.
Pathophysiology of EGPA
EGPA is an autoimmune condition in which the immune system mistakenly attacks blood vessels, leading to inflammation and tissue damage. It progresses through three stages:
Stages of EGPA
- Prodromal Phase: Characterized by respiratory symptoms such as asthma, allergic rhinitis, and sinusitis.
- Eosinophilic Phase: Marked by increased eosinophils infiltrating tissues, often leading to pulmonary complications and gastrointestinal symptoms.
- Vasculitic Phase: Blood vessel inflammation causes severe complications, including nerve damage, skin lesions, and organ dysfunction.
Causes and Risk Factors
While the exact cause remains unknown, EGPA is believed to arise from an abnormal immune response influenced by genetic and environmental factors. Key risk factors include:
- History of asthma or allergic rhinitis
- Genetic predisposition
- Environmental triggers such as infections or medications
- ANCA (anti-neutrophil cytoplasmic antibodies) positivity in some cases
Signs and Symptoms
Symptoms vary depending on the stage and organ involvement but commonly include:
- Respiratory: Asthma, sinusitis, lung infiltrates
- Neurological: Peripheral neuropathy, mononeuritis multiplex
- Gastrointestinal: Abdominal pain, gastrointestinal bleeding
- Skin: Purpura, nodules, rashes
- Cardiovascular: Myocarditis, pericarditis
- Renal: Glomerulonephritis in severe cases
Diagnostic Criteria and Tests
EGPA diagnosis involves clinical evaluation, laboratory tests, and imaging studies. Key diagnostic tools include:
- Blood Tests: Elevated eosinophil count, ANCA positivity
- Biopsy: Confirms vasculitis and eosinophilic infiltration
- Imaging: Chest X-rays, CT scans, MRI for organ assessment
- Electromyography (EMG): Evaluates nerve involvement
Treatment and Management
Treatment aims to control inflammation, prevent relapses, and manage symptoms. The standard approach includes:
1. Corticosteroids
- First-line therapy (e.g., prednisone)
- Rapid symptom relief but requires tapering to avoid side effects
2. Immunosuppressive Agents
- Cyclophosphamide or azathioprine for severe cases
- Methotrexate as a steroid-sparing option
3. Biologic Therapy
- Mepolizumab (IL-5 inhibitor) for eosinophilic inflammation control
- Rituximab for ANCA-positive cases
4. Supportive Treatments
- Bronchodilators for asthma management
- Anticoagulation for thrombosis prevention
- Physical therapy for neuropathy rehabilitation
Prognosis and Long-Term Outlook
With early diagnosis and proper treatment, EGPA prognosis has improved significantly. However, relapses are common, requiring long-term monitoring. Factors influencing prognosis include:
- Extent of organ involvement
- Response to therapy
- ANCA status (ANCA-positive cases may have more severe vasculitis)
