A 32-year-old woman complains of intermittent aching pains in the medial two fingers of both hands. During such episodes, the fingers become blanched and then blue. Her history is taken, and it is noted that she is a heavy smoker. The physician advises her that she must stop smoking and states that she will not prescribe any medication until the patient has discontinued smoking for a month. What is this patient's condition, and why was she told to stop smoking?