We report the case of a female patient who developed polymorphic expressions of neutrophilic dermatosis associated with p-ANCA while receiving benzylthiouracil for hyperthyroidism. A 41-year-old-woman was treated with benzylthiouracil for Basedow's disease. After 21 months of therapy, she developed fever with different expressions of neutrophilic dermatosis: pyoderma gangrenosum of feet, Sweet's syndrome of the forearms and the face. Biopsies confirmed the diagnosis of neutrophilic dermatosis. The histological examination of a skin specimen taken from the developing border of a foot lesion showed polynuclear neutrophilic infiltration with leucocytoclastic vasculitis and the presence of anti-myeloperoxydase p-ANCA. Abdominal ultrasound showed multiple splenic microabscesses. The myelogram, gastroscopy and colonoscopy findings were normal. Benzylthiouracil was stopped and systemic corticosteroid therapy resulted in regression of the skin lesions and splenic microabscesses. Different types of neutrophilic dermatosis were described in our case, confirming the notion of neutrophilic dermatosis continuum. The occurrence of neutrophilic dermatosis and p-ANCA after benzylthiouracil therapy suggests the involvement of polynuclear neutrophils in a common pathogenic mechanism. However, to date there have been no other reports analogous to ours, and inclusion of neutrophilic dermatosis as a benzylthiouracil-induced adverse effect would require confirmation by other instances of such associations.