Systemic vasculitis associated with eosinophilia and marked degranulation of tissue eosinophils

A 9-year-old girl had fever, life-threatening interstitial pneumonia, a vesicular skin rash, parotid and submandibular swelling, and marked blood eosinophilia (WBC count 47,000/microL, 39% eosinophils). Results of lung and skin biopsies showed vasculitis with intense eosinophil infiltration. Immunofluorescence analyses of these biopsies, as well as analysis of tissue from the parotid, lip, and trachea, showed striking deposition of eosinophil granule major basic protein associated with areas of tissue damage. Treatment with glucocorticoids and hydroxyurea produced clinical improvement. The association between tissue damage and deposition of the cytotoxic major basic protein suggests that the eosinophil contributed to the pathophysiology of this disease. Recognition of the capacity of the eosinophil to produce tissue damage can be helpful in the selection of therapy.