Zebra Hunting

Photo credit: Lesage Stefaan http://tinyurl.com/bpprqn6

Non-clinicians may not be familiar with “zebra” as a medical slang term.

Zebra is a medical slang term for a surprising diagnosis.[1] Although rare diseases are, in general, surprising when they are encountered, other diseases can be surprising in a particular person and time, and so “zebra” is the broader concept.

The term derives from the aphorism “When you hear hoofbeats behind you, don’t expect to see a zebra”, which was coined in a slightly modified form in the late 1940s by Dr. Theodore Woodward, a former professor at the University of Maryland School of Medicine in Baltimore.[2] Since horses are the most commonly encountered hoofed animal for most people and zebras are comparatively rarely encountered, logically one could confidently guess that the animal making the hoofbeats is probably a horse. By 1960, the aphorism was widely known in medical circles.[3]


There are times, though, when it makes sense to go looking for zebras.

Search engines like Google and database search (PubMed, EBSCO, whatever) rely on frequency and/or co-occurrence to rank search results, so common conditions are going to be easy to find and rank high in search results, while a rare disease/diagnosis  will not.

Enter FindZebra.

FindZebra is a specialised search engine supporting medical professionals in diagnosing difficult patient cases. Rare diseases are especially difficult to diagnose and this online medical search engines comes in support of medical personnel looking for diagnostic hypotheses. With a simple and consistent interface across all devices, it can be easily used as an aid tool at the time and place where medical decisions are made. The retrieved information is collected from reputable sources across the internet storing public medical articles on rare and genetic diseases.

FindZebra indexes 31,000 articles on rare and genetic diseases from these sources:

  • Orphanet: an online rare disease and orphan drug data base. Copyright, INSERM 1997. Available on www.orpha.net
  • Wikipedia: The free encyclopedia. Wikimedia Foundation, Inc., Category Rare Diseases. Available on en.wikipedia.org/wiki/Category:Rare_diseases
  • NORD Rare Disease Database and Organizational Database. The National Organization for Rare Disorders (NORD). Available on rarediseases.org/
  • The Genetic and Rare Diseases Information Center (GARD). Available on rarediseases.info.nih.gov/GARD
  • Swedish Information Centre for Rare Diseases. Swedish National Board of Health and Welfare. Available on www.socialstyrelsen.se/rarediseases
  • m-Power Rare Disease Database. Madisons Foundation. Available on www.madisonsfoundation.org/
  • Health On the Net Foundation. Available on www.hon.ch/HONselect/RareDiseases/
  • Rare Diseases. About.com Health. Available on rarediseases.about.com/
  • Genetics Home Reference: A service of the U.S. National Library of Medicine. Available on: ghr.nlm.nih.gov/BrowseConditions
  • Wikipedia: The free encyclopedia. Wikimedia Foundation, Inc., Category Syndromes. Available on en.wikipedia.org/wiki/Category:Syndromes
  • Online Mendelian Inheritance in Man, OMIM. McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University (Baltimore, MD) and National Center for Biotechnology Information, National Library of Medicine (Bethesda, MD). Available on www.ncbi.nlm.nih.gov/omim/
  • Wikipedia: The free encyclopedia. Wikimedia Foundation, Inc., Selected pages on rare diseases. Available on en.wikipedia.org/


To test FindZebra, I decided to search using the symptoms of a not-terribly-well-known condition called “Familial Mediterranean Fever.” My search string was: peritonitis fever inflamation 

Pretty cool results:



Because the site makes a point of repeating it, I’ll do the same:

WARNING! This is a research project to be used only by medical professionals.


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