EGPA Diagnostic Criteria: Comprehensive Overview

Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare vasculitis affecting small to medium-sized blood vessels, making its diagnosis crucial for effective management. Understanding EGPA’s diagnostic criteria is essential due to overlapping symptoms with other conditions.

Key Classification Criteria

The classification of EGPA relies on understanding its clinical and pathological features. The American College of Rheumatology (ACR) and the Chapel Hill Consensus Conference (CHCC) criteria emphasize asthma, eosinophilia, and systemic vasculitis. Asthma, often severe, is typically an early symptom. Eosinophilia, defined as an eosinophil count over 10% of total white blood cells, reflects the inflammatory process.

Systemic vasculitis involves multiple organ systems like the skin, lungs, gastrointestinal tract, and peripheral nerves. The ACR criteria require at least four of six features: asthma, eosinophilia, neuropathy, pulmonary infiltrates, paranasal sinus abnormalities, and extravascular eosinophils. These criteria differentiate EGPA from other vasculitis forms with high sensitivity and specificity.

Antineutrophil cytoplasmic antibodies (ANCA), particularly against myeloperoxidase (MPO), provide additional diagnostic clarity. ANCA-positive patients often show different clinical features, such as more frequent renal involvement, compared to ANCA-negative patients. This distinction influences diagnosis, treatment decisions, and prognosis.

Clinical Symptom Patterns

EGPA presents with diverse symptoms, often beginning with severe asthma. This respiratory distress, accompanied by allergic rhinitis, may initially suggest common allergic conditions. As the disease progresses, other organ systems become involved, complicating diagnosis. Cutaneous manifestations like palpable purpura or nodules are common, reflecting systemic inflammation.

Neurological complications, such as peripheral neuropathy, cause significant morbidity. This condition results from vasculitic damage, leading to pain, muscle weakness, and sensory loss. Gastrointestinal involvement, though less frequent, can present with abdominal pain or even bowel perforation. These symptoms necessitate a thorough evaluation.

Laboratory Testing

Laboratory testing is vital in diagnosing EGPA. A complete blood count (CBC) reveals eosinophilia, often exceeding 1,500 cells per microliter, indicating eosinophilic inflammation. Elevated serum immunoglobulin E (IgE) levels and inflammatory markers like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) support the diagnosis.

ANCA testing, especially for MPO-ANCA, adds diagnostic precision. While not all EGPA patients are ANCA-positive, its presence influences the clinical approach, especially regarding renal involvement.

Imaging Findings

Imaging studies provide insights into EGPA’s organ involvement. Computed tomography (CT) of the chest reveals pulmonary abnormalities like transient and migratory infiltrates. Magnetic resonance imaging (MRI) assesses neurological complications, offering detailed views of peripheral nerve damage. Positron emission tomography (PET) scans identify active inflammation across organ systems, guiding biopsies.

Differential Diagnosis With Other Vasculitides

Differentiating EGPA from other vasculitis forms requires understanding its unique combination of asthma, eosinophilia, and systemic vasculitis. Granulomatosis with polyangiitis and microscopic polyangiitis present similarly but lack EGPA’s eosinophilic component and allergic features. ANCA type and clinical presentations help distinguish these conditions, impacting management and treatment strategies.