Immunological Markers Associated with Skin Manifestations of EGPA

Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare systemic vasculitis with eosinophilic inflammation and variable clinical presentations. Although skin manifestations are frequent, current classification criteria do not include them, which may underestimate their diagnostic value. This prospective observational study aimed to assess systemic and skin involvement as well as eosinophilia, anti-neutrophil cytoplasmic antibody (ANCA), and Anti-nuclear antibodies (ANA) serum levels in 20 EGPA patients followed for one year at the University Hospital of Messina, Italy, before starting Mepolizumab, 300 mg. Eosinophilia, ANCA status, systemic and skin involvement were also evaluated at 6 and 12 months; a literature review on these data supplements our findings. Skin involvement was present in 55% of patients, including purpura, urticarial vasculitis, angioedema, maculopapular rash, and nodules, mostly in ANCA-negative patients, though purpura was more frequent in ANCA-positive cases but without any statistically significant correlation. ANAs were present in 50% of patients, together with ANCA in two subjects and without in eight. Mepolizumab significantly reduced eosinophil levels, BVASs, and corticosteroid dependence, with notable improvement in skin symptoms. In conclusion, skin manifestations are common in EGPA and may represent useful indicators of disease activity. Their integration with ANCA status, eosinophil counts, and positivity to other autoantibodies could enhance diagnostic and monitoring strategies identifying different clusters of EGPA patients even if the small sample size limits the generalizability of the findings.