On the definition of dermatological disease. Part 1: conceptual frameworks.

Little attention is paid to disease definition in dermatology and how such definitions come about, yet defining a disease is a fundamental step upon which all subsequent clinical management and prognostic judgements depend. Developing diagnostic criteria is also a critically important step for research purposes so that studies referring to groups of people can be compared in a meaningful way. This short review introduces the concepts of regressive and progressive nosology, and how definitions of a dermatological disease can evolve in a useful way as knowledge about that disease increases. It also highlights the dangers of panchrestons - names that try to explain all yet end up explaining very little. It also considers approaches to disease definition, such as whether a binary yes/no or continuous approach is more appropriate. Conceptual frameworks including essentialistic vs. nominalistic approaches using the biomedical or biopsychosocial perspectives are articulated. The review then illustrates hazards of underdiagnosis and overdiagnosis, and introduces the notion of 'disease mongering' - the selling of disease in order to promote the use of medicines. The review concludes with a reaffirmation of the importance of defining dermatological disease, and why any new diagnostic criteria must be shown to increase predictive ability before they are assimilated into clinical practice and research.