A 58-year-old woman with ulcerative colitis of 5 years' duration was first seen in March 2002 with a 5-month history of widespread erosions on the palate and gingiva, subtle scarring of the conjunctiva, and xerostomia accompanying a flare of ulcerative colitis. No skin lesions were observed. Direct immunofluorescence study performed on the oral mucosa showed a linear distribution of immunoglobulin G (IgG) and immunoglobulin A (IgA) at the dermal-epidermal junction. Indirect immunofluorescence demonstrated the presence of circulating IgG anti-basement membrane zone antibody. This patient was successfully treated with sulfasalazine 3 g/day. Two years later, however, she developed extensive, well-defined pustules and vegetating erosions on the skin, symmetrically localized in the inguinal and axillary folds and on the upper inner thighs (Fig. 1). At that time, mucous membrane involvement, except for subtle scarring conjunctivitis, was not observed. Laboratory findings were normal, except for colonoscopy, which disclosed cobblestoning and histologically well-circumscribed granulomas, confirming the diagnosis of ulcerative colitis. On the basis of the clinical features and the flare of coexistent ulcerative colitis, this patient was suspected of having pyoderma gangrenosum. Skin biopsy specimens showed acanthosis, papillomatosis, pseudo-carcinomatous hyperplasia, and subepidermal blisters overlying an infiltrate of leukocytes and eosinophils, which also extended into the lower epidermis (Fig. 2). Direct immunofluorescence of the perilesional skin demonstrated a linear distribution of IgG and IgA at the dermal-epidermal junction. In vivo-bound IgG within the basement membrane zone was documented using laser scanning confocal microscopy, which disclosed the presence of immunoglobulins above collagen type IV and below laminin-5 (Fig. 3). Indirect immunofluorescence study showed the presence of circulating IgG anti-basement membrane zone antibody reacting with the roof and floor of salt-split skin. Characterization of the target antigen (courtesy of Professor Hashimoto of Kurume University, Kurume, Japan) was unsuccessful, as Western immunoblot study on both epidermal and dermal extracts was negative, as was immunoblot with purified laminin-5 and enzyme-linked immunosorbent assay with the NC16a epitope of BP180. Laser scanning confocal microscopy confirmed the diagnosis of cicatricial pemphigoid. Therapy consisting of prednisone 40 mg each morning and sulfasalazine 1.0 g three times daily led to rapid improvement of the skin lesions, but did not affect the conjunctival lesions. After 4 weeks, prednisone was tapered and sulfasalazine was continued at a reduced dose of 0.5 g three times daily. At that time, only post-inflammatory hyperpigmentation and atrophic scars were evident.