Here’s one of those medical mysteries from a New England Journal CPC. Although it should never actually be a mystery---it’s easy to diagnose if you think about it---it remains under appreciated. It’s a must not miss diagnosis.
If you haven’t read the CPC, test yourself. To play the game it’s enough to know that this patient presented in cardiac arrest. Without peeking (that is don’t scroll down too far) click on Figure 1 and click again to zoom. You should have the correct diagnosis in mind in seconds.
This is not a typical CPC case because it’s a look-see diagnosis. Although the discussant goes through the obligatory long differential diagnosis (and a brilliant discussion it is!) he indicates from the start that the exercise isn’t really necessary. He opens his discussion of differential diagnosis by saying “Although I am aware of the diagnosis in this case……..” It is, of course, Brugada syndrome.
Here are some additional useful resources.   These latter are open access full text in case you can’t access the NEJM CPC.