Hypochondriac (hī-pō-kon’drē-ak): a person with somatic over-concern, including morbid attention to the details of bodily functioning and exaggeration of any symptoms no matter how insignificant. (http://www.thehypochondriac.com/)

This is a disorder that is based on the idea that a person is overconcerned about sickness. Even after a physician has told the person they aren't ill, the person will still believe that they are. People with this disorder will think the slightest of pains or aches is because of a disease such as AIDS or cancer.