The famous medical aphorism goes something like, “When you hear hoof-beats, think horses, not zebras.”  i.e. Don’t go searching for obscure conditions, because it’ll cost lots of time & money.  Clinicians love to tout their trophy diagnoses.

A corollary notes, “When faced with a diagnostic challenge, first consider unusual presentations of common diseases rather than classic manifestations of rare ones, because common diseases occur commonly, and rare ones rarely.”

Am not sure I completely agree.  But certainly, you’ll never find a rare [possibly lethal??] condition if you never think of it.  Entertaining unusual possibilities keeps our minds active.  How sad, if for every bad back, all we did was hand out ibuprofen [or Oxycontin] & move on to the next.