Why the zebra?
"When you hear hoofbeats behind you, don't expect to see a zebra.”
The zebra became the symbol of rare diseases because of this expression coined in the late 1940s by Dr. Theodore Woodward, professor at the University of Maryland School of Medicine in Baltimore.
A principle for young doctors
Since horses are the most commonly encountered hoofed animals and zebras are rare, logically one can assume that the animal making a hoofbeat noise is probably a horse. This is what Dr. Woodward wanted to convey to his students about diagnosing a disease: when faced with symptoms in a patient, think of a horse, not a zebra.
Dr Woodward believed that doctors in training had a predisposition to make rare diagnoses. In fact, like all of us, they tend to remember events that are out of the ordinary. Thus, the “zebra-horse” concept has a valid role in teaching medical students to be better diagnosticians.
If it's not a horse, then it's a zebra
However, when no common disease is confirmed in the patient, the doctor should continue his search: all or part of the symptoms present may correspond to one or other of the 7,000 known rare diseases or even to a disease not characterized until now. It is true that doctors cannot know all these diseases. So it takes time and effort.
The diagnostic odyssey
However, the failure to think of the zebra first when diagnosing, the fact that there are so many different rare diseases, and the reality of the working conditions of doctors in our healthcare system, results in long delays in diagnosis. Some individuals may never know in their lifetime what disease afflicts them. Patients often experience a long “diagnostic odyssey”: going from one doctor to another for many years to find an answer; a journey accompanied by false hopes. The absence of diagnosis can have an impact on the person’s care, and undeniably, it leads to distress due to a lack of therapeutic hope.
A survey by the RQMO of people with a rare disease and parents of affected children in Quebec showed that:
- For 37 % of individuals who know their disease or that of their child, it took 3 years or more to obtain the diagnosis;
- For 18 % of them, more than 10 years have passed.
(Out of 259 respondents who answered this question)
The zebra feels lonely among the horses
Due to the rarity of their disease, rare patients feel alone compared to the many people suffering from common diseases, even though there are approximately 700, 000 people in Quebec affected by one or other of the 7,000 rare diseases. The lack of information about the disease, the lack of knowledge on the part of health professionals, the fact of not knowing other similar patients, the lack of research and therapeutic development, the lack of understanding of those around them, etc. are all factors which contribute to the isolation of the zebra.
In the survey, 73% of individuals or parents struggling with a rare disease said they “felt alone with illness”(out of 243 respondents who answered this question).
