Eosinophilic granulomatosis with polyangiitis
The American College of Rheumatology (ACR) provides 6 classification criteria, of which 4 are required for diagnosis (sensitivity 85% and specificity 99%):
- Peripheral blood eosinophilia >10%
- Migratory pulmonary infiltrates
- Paranasal sinus abnormalities
- Tissue eosinophils
Three, often overlapping, phases have been described in the clinical course of EGPA: a prodromal allergic phase, an eosinophilic phase, and a vasculitic phase.
The prodromal phase may last months to years, with asthma as the main manifestation (96%-100% of patients). Also common in this phase (47%-93% of patients) are allergic rhinitis, sinusitis, and nasal polyposis. (Nasal granulomas, hemorrhage, and crusting are seen in granulomatosis with polyangiitis [formerly called Wegener granulomatosis].)
An elevated eosinophil count defines the second phase, and the onset of vasculitis with involvement of the peripheral nervous system marks the third phase.
While 62% of cases have cardiac involvement, clinical symptoms are only reported in 26% of cases. However, cardiac involvement remains the primary cause of death.
Cutaneous findings are common and can range from erythema, petechiae, and extensive ecchymosis, to nodules, urticaria, and vesicles. Livedo reticularis may also be seen.
Although still considered idiopathic, recent research indicates that eosinophil infiltration and antineutrophil cytoplasmic autoantibody (ANCA)-induced endothelial damage may be involved in the underlying disease mechanism. These are believed to be triggered by an unknown infectious agent, allergens, vaccinations, medications (leukotriene receptor antagonists), a foreign antigen, or an auto-antigen in predisposed individuals. Recently, it has been suggested that 2 distinct phenotypes of EGPA are present and depend on the presence or absence of ANCA antibodies.
The average onset of disease is in the third to fifth decade of life with slight male predominance, with overall yearly incidence of 0.11-2.66 million and prevalence of 10.7-14 million. Of note, recent pediatric studies have even reported EGPA in children as young as 4.
M30.1 – Polyarteritis with lung involvement [Churg-Strauss]
82275008 – Churg-Strauss syndrome
- Chronic eosinophilic pneumonia is the condition that should be considered first because it is more common and has less severe clinical outcomes. The degree of eosinophilia is not as great as EGPA and necrotizing vasculitis and granulomas are not present.
- Hypereosinophilic syndrome is another condition with features that overlap with EGPA (multi-system and persistent blood and marrow eosinophilia). However, the key findings that distinguish it from EGPA are the absence of asthma, vasculitis, and granulomas.
- Bronchocentric granulomatosis is a rare condition associated with allergic bronchopulmonary aspergillosis (ABPA). Patients may have asthma, necrotizing granulomas, blood eosinophilia, and eosinophilic pneumonia. However, unlike in EGPA, the granulomatous inflammation is limited to bronchocentric location with accompanying mucoid impaction of bronchi and Charcot-Leyden crystals and fungal hyphae. Necrotizing vasculitis is almost always absent.
- Granulomatosis with polyangiitis in rare cases presents with eosinophilia in the lung tissue and blood. However, none of the patients have asthma or lung findings similar to eosinophilic pneumonia.
- Other conditions to rule out that present with tissue eosinophilia and granulomatous inflammation include coccidioidomycosis, dirofilarial nodules, eosinophilic vascular infiltration of pneumothorax, Löffler syndrome, viral / bacterial / fungal pneumonia, and eosinophilic granuloma.
Last Updated: 06/05/2017