Disease can be manifest in a number of ways. Sometimes, the condition produces manifestations, such as fever, that make it evident that the person is sick. Other diseases are silent at the onset and are detected during examination for other purposes or after the disease is far advanced.
Signs and symptoms are terms used to describe the structural and functional changes that accompany a disease. A symptom is a subjective complaint that is noted by the person with a disorder, whereas a sign is a manifestation that is noted by an observer. Pain, difficulty in breathing, and dizziness are symptoms of a disease. An elevated temperature, a swollen extremity, and changes in pupil size are objective signs that can be observed by someone other than the person with the disease. Signs and symptoms may be related to the primary disorder, or they may represent the body's attempt to compensate for the altered function caused by the pathologic condition. Many pathologic states are not observed directly—one cannot see a sick heart or a failing kidney. Instead, what can be observed is the body's attempt to compensate for changes in function brought about by the disease, such as the tachycardia that accompanies blood loss or the increased respiratory rate that occurs with pneumonia.
It is important to recognize that a single sign or symptom may be associated with a number of different disease states. For example, an elevated temperature can indicate the presence of an infection, heat stroke, brain tumor, or any number of other disorders. A differential diagnosis that describes the origin of a disorder usually requires information regarding a number of signs and symptoms. For example, the presence of fever, a reddened sore throat, and positive throat culture describe a "strep throat" infection. A syndrome is a compilation of signs and symptoms (e.g., chronic fatigue syndrome) that are characteristic of a specific disease state. Complications are possible adverse ex-
