Progression of classic Kaposi's sarcoma with rituximab.

Rituximab is a monoclonal antibody directed against the CD20 antigen of B cells and is being used increasingly for treatment of antibody-mediated autoimmune diseases. We observed the rapid progression of Kaposi's sarcoma after our patient received rituximab for autoimmune hemolytic anemia. We postulate that by very specifically depleting B cells, rituximab affects T-cell function (eliminating B- and T-cell interactions), resulting in impaired T-cell-mediated immunity. Dermatologists should use caution when offering rituximab for off-label use.