Doctors often portray diseases as syndromes, living illustrations of which are labeled cases. That students often perceive diseases as puzzles to be solved is therefore unsurprising. However, away from the ivory tower of Grand Rounds, diseases may not be so clearly bar-coded. Patients recover or die without a diagnosis, overlap syndromes occur, multiple pathologies coexist, spontaneous and functional phenomena are freely invoked. The notion of disease as a pure clinicopathologic entity is thus blurred in practice.

In recent years this muddle has been clarified by the insight that genetic mutations may contribute to a disease phenotype; for example, the discovery of mutations in the rhodopsin gene transformed retinitis pigmentosa from a Corridor Curiosity to a Textbook Tutorial. This change in outlook has brought science and medicine together. Articles concerning human disease now flood into scientific journals, just as gene sequence depositions are drifting into medical journals. In clinical textbooks molecular explanations are supplanting bedside descriptions, whereas primers of molecular biology often use human diseases to enliven their bloodless subject matter.