Why the Zebra?

“When you hear hoofbeats, think horses, not zebras.”

This phrase is told to medical students throughout their training.

In medicine, the term “zebra” is used in reference to a rare disease or condition.

Doctors are taught to assume that the simplest explanation is usually the best, so as not to go around diagnosing patients with all sorts of exotic illnesses that are highly unlikely.  Common diseases (i.e. the horses) are what doctors should expect to encounter.

Many doctors seem to forget however, that “zebras” do exist, and so getting treatment can be more difficult for sufferers of rare conditions and diseases.