Eosinophilic infiltration: an under-reported histological finding in urticarial vasculitis

Area of Science:

• Dermatopathology
• Immunohistochemistry
• Histology

Background:

• Urticarial vasculitis (UV) presents clinically as urticaria but with prolonged lesion duration and purpura.
• Differentiating UV from common urticaria is crucial for appropriate patient management.

Purpose of the Study:

• To identify and evaluate distinguishing histological features between urticarial vasculitis and common urticaria.
• To improve diagnostic accuracy for these two skin conditions.

Main Methods:

• Histological assessment of 245 UV samples and 55 urticaria samples over one year.
• Selection criteria included confirmed UV diagnosis by dermatopathologists and discrepancy with clinical impression.

Main Results:

• Endothelial swelling (96%), red blood cell (RBC) extravasation (18%), and neutrophilic infiltration (46.7%) were observed in UV.
• Significant differences between UV and urticaria included endothelial cell swelling, perivascular neutrophils, and eosinophilic infiltrations (P < 0.001).
• Both conditions predominantly showed lymphocytic infiltration; only 0.8% of UV cases had predominant neutrophilic infiltration.

Conclusions:

• Urticarial vasculitis and urticaria share lymphocytic infiltration, but UV also exhibits RBC extravasation, endothelial swelling, and fibrin deposition.
• Significant eosinophilic infiltration (perineural, perivascular, interstitial) in UV lesions suggests a role in its pathogenesis.
• Histological analysis is vital for distinguishing UV from urticaria, highlighting the importance of eosinophils and endothelial changes.