Demonstration of antibody to 230 kDa bullous pemphigoid antigen in lichen planus-like keratosis.

We describe a 67-year-old man with lichen planus-like keratosis associated with anti-230 kDa bullous pemphigoid antigen (BPAG1) autoantibody. The patient had noticed solitary dark brown macule more than 6 years previously on his left chest. Histological findings showed hypergranulosis, irregular acanthosis, liquefaction degeneration of basal cells, band-like infiltration of lymphocytes at the subepidermal portion, and a cleft at the basement membrane zone (BMZ), resulting in the formation of subepidermal blisters. Direct immunofluorescence findings of perilesional skin showed a linear deposition of IgG at BMZ. On indirect immunofluorescent study using normal human skin, circulating IgG autoantibody to BMZ was present in the patient's serum at a titer of 1:80. The antigen located on the epidermal site of normal skin split by 1M NaCl was reacted with the patient's serum. Immunoblot analysis using epidermal extracts demonstrated the presence of IgG antibody directed to BPAG1 in the patient's serum. These observations suggest that the presence of an antibody to BPAG1 could be caused by the damage of basal cells following lichen planus-like keratosis.