The Knox County Sheriff’s Department is looking for a missing West Knox County man who has medical problems. Officers say 78-year-old John Preston left his home on Venice Road and has not been seen since. Preston is described as a Caucasian male standing 6 feet tall, weighing 175 pounds with silver hair, a thin build and wears glasses. He is diabetic and has cardiac issues. He was last seen driving a tan 2010 Chevrolet Equinox with Tennessee tag 208-MWV. Anyone with information about Preston is asked to call the Knox County Sheriff’s Office at 865-215-2243 or 911.