We specialists in infectious diseases love case conferences — especially those where the case is presented as an “unknown,” and we try to figure out the diagnosis from the history.

I suppose this isn’t very surprising, since ID cases in general are already among the most interesting in all of medicine. Those that are case-conference-worthy are particularly prime.

“Funny bug in a funny place,” was how one of my colleagues characterized these cases.

After the case is presented, the discussion by the participants takes various forms. I’ve been to hundreds of these conferences over the years, and have noted that the path taken by the discussants to arrive at the diagnosis (or not) varies quite a bit. There are certain styles, certain patterns of medical thinking in the conference room (rather than in the exam room or at the bedside) that show up again and again:

• The instinctual, “Here’s the diagnosis” approach. Very valuable when spoken by the giants in the field, who usually have several decades of clinical experience. These are short, targeted discussions that impressively even list the possible diagnoses in order of likelihood. Lou Weinstein was the quintessential “here’s the diagnosis” guy; sadly I only got to hear him discuss cases in the last few years of his distinguished career. Not surprisingly, this kind of medical reasoning doesn’t work nearly as well when attempted by relative beginners, e.g., a medical student, or even a second-year ID fellow. Bottom line: Beware the clinician in his/her 20s who begins a case discussion with the phrase, “In my clinical experience …”
• The comprehensive, “I’ve considered the entire universe of living organisms” approach. Can be both spectacularly interesting and educational or, conversely, crushingly, mind-numbingly boring. Mort Swartz (another giant in the field) discusses cases in this style, and I learn something from Mort every time — his knowledge not only of ID but all of internal medicine is awe-inspiring. However, my heart always sinks when a mere non-Mort mortal (couldn’t resist) starts a discussion by listing all the main categories of microorganisms as a prelude:  “Let’s see, as potential causes for this person’s infected hip, there are prions, viruses, aerobic and anaerobic bacteria, higher bacteria, mycobacteria, fungi, algae, protozoa, helminths, ectoparasites …” Time to get some more coffee.
• The prodding, “Let’s stop this game and tell me the diagnosis” approach. Usually goes something like this: A generic case is presented with minimal information — let’s say a man with a skin infection. No further history is given. And the discussant, not surprisingly, prods the presenter to give more information. “Any cats?” he/she asks, thinking Pasturella multocida or bartonella. “Any water exposure?” thinking Aeromonas hydrophila or Vibrio vulnificus. Because the discussant knows a simple skin infection is never going to make it to case conference, he/she keeps searching — there MUST be something interesting about the epidemiology. The presenter relents: “Well, as it turns out, the patient works as a clam shucker.” Bingo, Mycobacterium marinum or Erysipelothrix rhusiopathiae.
• The diverting “I don’t know what this diagnosis is, but I certainly know a lot about other stuff, so let’s talk about that” approach. This clever strategy usually involves a true expert in a field forced out of his or her comfort zone. The world expert on salmonella, for example, suddenly finds him/herself discussing a hospital-acquired pneumonia in a patient who’s just had cardiac surgery. You can be sure that eventually the subject of intracellular pathogens (of which salmonella is an excellent example) will come up — somehow.
• The deer in a headlights, “You talking to me?” approach. Happens frequently when someone gets called on to discuss a case who’s not expecting it. Perhaps they’re junior faculty. Or just shy. Or maybe their mind has wandered, and they’re thinking about the Patriots’ playoff game, or whether to have another muffin, or the Krebs cycle. And I’ve been informed by one of my most esteemed colleagues that some people just hate being called on, which I totally respect. (But others love yacking away during conference — they get offended if they’re not asked to opine — so it would be helpful to know how people feel about this. A green sticker on your white coat, perhaps, one that reads, “CALL ON ME!”) Suffice to say the startled discussant rarely gets the diagnosis correct, but they are often inadvertently funny.

Here’s a tip — if you’re ever asked about a case during conference, and you haven’t been listening, and the person being discussed is acutely ill, just say, “It could be staph.” If chronically ill, “It could be TB.” You will never be wrong.

What kind of discussant are you?

Paul Sax is the Clinical Director of Infectious Diseases at Brigham and Women’s Hospital. His blog HIV and ID Observations, is part of Journal Watch, where he is Editor of Journal Watch AIDS Clinical Care.

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