Localised bullous pemphigoid overlying knee arthroplasty: a diagnostic challenge

An elderly Caucasian woman developed bullous pemphigoid (BP) overlying the site of total knee arthroplasty for osteoarthritis 2 days after surgery. The clinical findings were consistent with blistering due to soft tissue swelling, bullous impetigo or allergic contact dermatitis. The blistering spread over weeks to months down the ipsilateral leg and then to the other leg and hips. A biopsy for H&E and direct immunofluorescence established the diagnosis of BP. A concomitantly occurring wound infection was identified and treated. The blistering responded well to superpotent topical steroids and local care.