Time-course analyses of exercise-induced lesions in a patient with urticarial vasculitis.

Using immunoperoxidase techniques, we examined the histological changes of exercise-induced lesions of urticarial vasculitis over a 24 h period. At 3 h, endothelial swelling and an eosinophilic infiltrate was seen. Neutrophils were increased in number by 10 h. Typical leucocytoclastic vasculitis with red blood cell extravasation developed by 24 h. Maximal deposition of eosinophil peroxidase was at 10 h compared to significant neutrophil elastase deposits at 24 h. This demonstrates the importance of the eosinophil in the development of the lesions of urticarial vasculitis.