Mast Cells in Cutaneous Allergic Vasculitis: A Case Report

Background: The mechanism of cutaneous allergic vasculitis still remains unclear, and to the best of our knowledge, no case has been reported in the literature in which the number of mast cells was examined. Methods: A 33-year-old woman, with a past history of allergic rhinitis due to Japanese cedar and Phleum pratense (timothy), presented with a chief complaint of palpable papules on both lower legs in December 2002. On blood examination, peripheral blood eosinophilia was present, but all other examinations for immunologic diseases were negative, including specific IgE. We suspected cutaneous allergic vasculitis and performed skin biopsy. Results: In December 2002, histological examination of biopsy specimens of the skin lesions showed leukocytoclastic vasculitis. The diagnosis of cutaneous allergic vasculitis was made based on the clinical symptoms and the pathological findings of biopsy specimens. Immunohistochemical staining for human mast cell tryptase using monoclonal antibody against human mast cell tryptase showed an accumulation of mast cells. Treatment with oral corticosteroid resulted in the disappearance of clinical symptoms, and the steroid tapered. A second skin biopsy was performed in June 2005 after informed consent was obtained. Histological examination showed no findings of leukocytoclastic vasculitis, and the number of mast cells had decreased. She has been well without treatment. Conclusions: Mast cells may increase in the skin lesion of cutaneous allergic vasculitis