Susan M. Turley, MS

Half way through a 15-minute iontophoresis treatment for de Quervain tenosynovitis of the right wrist, a 42-year-old woman felt exquisite pain but completed the session. After the therapist returned to the room and removed the electrodes, a light gray circular mark about 5 mm in diameter was noted on the skin. The epidermis was gone, and the underlying dermis was also injured. Within 6 hours, a tender, dark red-brown lesion developed.