The mechanism of anti-CD20-mediated B cell depletion revealed by intravital imaging.

Since the first description of paraneoplastic pemphigus, several cases have been described in the literature. However, curative therapy is usually a challenge to the physicians treating this disease. Several publications are available discussing the efficacy of steroids, cyclophosphamide and cyclosporin A. Recently, a report of the successful use of rituximab was also published. However, the use of cyclosporin A is controversial in the case of B cell malignancies, as there are reports showing the cytotoxic effect of this drug on B cells. However, other authors report no effect, or even unwanted effects resulting in B cell proliferation. We report the case of a 50-year-old Caucasian male. He developed a B cell lymphoma consisting of CD5/CD20-double-positive cells, and 2 months later, it was followed by a very severe paraneoplastic pemphigus affecting the mucosa and the skin. The lymphoma was well managed with CHOP and CVP polychemotherapy, followed by oral chlorambucil; however, the bullous eruptions did not disappear. Oral steroids, cyclophosphamide, plasmapheresis and IVIG therapy were only partially successful, so we decided to use oral cyclosporin A. Starting with 7 mg/kg and maintaining a steady plasma level of no less then 110 ng/l, the bullae completely disappeared within 6 weeks, and the patient has been in remission for 17 months now, taking the oral cyclosporin A continuously. The underlying B cell disorder did not relapse during the therapy.