THE CONCEPT OF DISEASE

THE CONCEPT OF DISEASE

What is disease? Some have defined it as the condition in which the normal function of some part or organ of the body is disturbed. Others have maintained that disease does not exist except as a reaction to injury. These definitions are both valid and in no way mutually exclusive. Any individual disease can usefully be regarded, in terms of simple set theory, as the common set of a number of sets, most notably type of injury, type of reaction and the location of injury. One can expand this simple concept to cover situations in which cells, tissue or organs are acted upon unfavourably either by injurious agents or by inborn errors acting alone or in conjunction of events that follows may be dominated by the direct effects of the injurious agent on the cell (as in certain chemical injuries), or may be a combination of these direct effects, and the local and general cell and tissue reactions that may be elicited.

            The functional disturbances produced by injury to cells are often mirrored by structural changes (a lesion), just as, in turn, structural damage may be followed by loss or alteration of some normal function. The sum of these effects finds its expression in the symptoms experienced by the patient and the signs observed by the physician.