Elevated eosinophils play a key role in EGPA

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare disease defined by eosinophil-rich and necrotizing granulomatous inflammation, and necrotizing vasculitis predominately affecting small to medium vessels.1-3

Formerly known as Churg-Strauss syndrome, EGPA often involves the respiratory tract, and patients frequently have asthma, sinusitis, and pulmonary infiltrates.1-3

Eosinophils diagram

Formerly known as Churg-Strauss syndrome, EGPA often involves the respiratory tract, and patients frequently have asthma, sinusitis, and pulmonary infiltrates.1-3

Prevalence and onset

Based on global estimates, EGPA likely affects approximately 5,000 people in the United States.4,5*

The average age range for onset is between 40 and 60 years old. However, onset can occur prior to age 40.6,7

It may take a while to diagnose EGPA.

It may take a while to diagnose EGPA.

The average time between disease onset and diagnosis is approximately 49.7 months (±6.1 months).7

*The US estimate is derived from a global summary prevalence of 14.58 cases per million, based on a US population of approximately 328 million people as of July 2019.4,5

The 3 phases of EGPA

EGPA is classically described as a 3-phase disorder6,8,9:

1

Prodromal

Severe asthma (typically adult onset) and allergies

2

Eosinophilic

Peripheral blood eosinophilia

3

Vasculitic

Necrotizing vasculitis and granulomas

Not all patients experience all phases, and these phases may overlap.

Goal of EGPA treatment

The current standard of care (SOC) is oral corticosteroids (OCS) with or without an immunosuppressant. According to EGPA guidelines, the goal of therapy in EGPA is to increase remission and reduce relapse rates while tapering OCS dose.10

Clinical manifestations of EGPA vary depending on organ involvement

All EGPA patients are different. Patients may present with single- or multiple-organ involvement. Organs and organ systems that may be impacted by EGPA include7-9:

Organs that may be impacted by EGPA diagram
Organs that may be impacted by EGPA diagram

Classification of EGPA using the ACR classification criteria1*

Presence of ≥4 of the following criteria yields a sensitivity of 85% and a specificity of 99.7% for EGPA1:

Asthma

Eosinophilia
(>10% of white blood cell count)

Mononeuropathy or polyneuropathy

Transient pulmonary infiltrates on chest x-rays

Biopsy showing extravascular eosinophils

Paranasal sinus abnormalities

*In 1990, the American College of Rheumatology (ACR) developed criteria that classified patients diagnosed with system vasculitis into a specific subset. These criteria are meant for classification and not diagnostic purposes.

Possible diagnostic evaluations

Laboratory and imaging tests (based on patient presentation)9-11

  • Complete blood count (CBC) with differential to evaluate eosinophil count
  • Urinalysis
  • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level
  • Pulmonary function tests
  • Electromyography and nerve-conduction studies
  • Electrocardiogram, N-terminal probrain natriuretic peptide (NT-proBNP), and troponin I measurements
  • CT scans, MRI, ultrasound as needed

ANCA detection10,12-15

EGPA is an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. ANCA positivity is observed in up to 40% of patients with EGPA.

  • A combination of immunofluorescence and enzyme-linked immunosorbent assays (ELISA) are used to maximize sensitivity and specificity for diagnosis
  • ANCA positivity is suggestive of the disease in the appropriate clinical setting, but ANCA negativity does not rule out the disease
  • Some data suggest there are different EGPA phenotypes based on ANCA status; however, more study is needed

Biopsy10-12

  • Although biopsy is the gold standard, most patients do not undergo biopsy and are diagnosed on a clinical basis
  • While skin, nerve, and muscle are among the tissues most often biopsied, endomyocardial, renal, and gastrointestinal biopsies may be useful as well
  • A biopsy containing a blood vessel with extravascular eosinophils supports a diagnosis in the context of other clinical manifestations of EGPA

Differentiating EGPA from HES

Characteristics and clinical manifestations of EGPA overlap with those of hypereosinophilic syndrome (HES). See below for similarities and differences between these two conditions.16

  Features of EGPA include:   Features of HES include:
  Eosinophilia >10%6     Peripheral blood hypereosinophilia (>1500 cells/μL on ≥2 occasions at least 1 month apart)17
  Eosinophil-rich, necrotizing granulomatous vasculitis affecting small-to-medium sized vessels2     Vasculitic complications are rare6
  Frequent asthma and nasal polyps6     Pulmonary manifestations occur; presence of asthma and nasal polyps is rare6
  ~40% of patients have ANCA antibodies10,12   ANCA-negative6
  Patients may experience systemic manifestations   Patients may experience systemic manifestations