Historically, doctors have diagnosed and classified diseases by their symptoms. In the future, however, medical professionals may classify diseases by their genetic underpinnings. For example, boys with Duchenne muscular dystrophy have a similar set of genes active as adults who have heart attacks. Such research is already starting to change the practice of nosology, the field of disease classification. Article [1]
Links:
[1] http://www.nytimes.com/2008/05/06/health/research/06dise.html?ref=health