EGPA Phenotyping: Not Only ANCA, but Also Eosinophils

Area of Science:

• Immunology
• Rheumatology
• Pulmonology

Background:

• Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a small-vessel vasculitis.
• Anti-neutrophil cytoplasmic antibodies (ANCA) are established biomarkers for EGPA phenotypes.
• The role of blood eosinophil count (BEC) in defining EGPA phenotypes remains unclear.

Purpose of the Study:

• To investigate the utility of BEC as a biomarker for differentiating EGPA phenotypes.
• To correlate BEC levels with specific clinical manifestations and organ involvement in EGPA patients.

Main Methods:

• Retrospective analysis of 168 EGPA patients from an Immunology Clinic.
• Collection of demographic, laboratory, and clinical data.
• Logistic Regression analysis to assess the predictive power of baseline features for EGPA phenotypes.

Main Results:

• Low BEC (≤1500 cells/mL) predicted a respiratory-limited phenotype (asthma, CRSwNP, lung opacities).
• High BEC (>3500 cells/mL) predicted a systemic phenotype with extrapulmonary organ involvement.
• BEC also predicted peripheral nervous system (PNS) involvement; ANCA positivity predicted extrapulmonary involvement.

Conclusions:

• Two distinct EGPA phenotypes, systemic and respiratory-limited, can be identified based on BEC.
• These phenotypes exhibit different organ involvement patterns and potentially different prognoses.
• BEC serves as a valuable biomarker for EGPA phenotyping, independent of ANCA status.