“Differential diagnosis, people!” On TV's “House,” medical sleuth Dr. Gregory House and his team try to get to the bottom of patients' mysterious ailments — with House testily demanding his colleagues determine every possible disease they could be dealing with. The challenge, of course, is that one set of symptoms can represent a number of different afflictions (hence the reason House's colleagues usually offer lupus — which has similar symptoms to practically every other malady — as the differential diagnosis).