Rare or orphan diseases
A rare disease is a disease that affects less than 1 in 2,000 people in the population
A rare disease is a disease that has a low frequency in the population. The most common definition of a rare disease is: a disease that affects fewer than 1 in 2,000 people in a population (in the United States, it is defined as a disease that affects fewer than 200,000 people in the population). Examples of rare diseases: cystic fibrosis, Duchenne muscular dystrophy, Huntington’s disease, autoimmune myasthenia gravis, Angelman syndrome, Ewing’s sarcoma, borreliosis, etc. The vast majority of rare diseases have a frequency of less than 1/100,000 people in the population. These are often called “utra-rare”. Thousands of rare diseases have been identified worldwide. While each disease is rare, all together they affect many people. According to some estimates, these represent 25% to 35% of all human diseases. See below the definition of an orphan disease.
There are more than 7,000 rare diseases
Depending on the source, it is said that there are between 7,000 and 8,000 rare diseases. It depends on the databases that list them and the definition of a disease. New diseases are characterized regularly, especially thanks to genomic technologies. In 2023, the Orphanet portal lists more than 6,000 rare diseases and OMIM (Online Mendelian Inheritance in Man) lists about 7,000 diseases (only those of genetic origin). Since the year 2000, efforts in analysing various databases and the inclusion of diseases identified by the new genomic technologies have resulted in an estimate of about 10,000 rare diseases. (Estimating the number of rare diseases – the concept of rare, ultra-rare and hyper-rare, 2022)).
40% to 50% of sick individuals do not have a diagnosis
An individual may suffer from an illness that doctors cannot identify. Usually, an undiagnosed disease is a rare disease. It is said that at any given moment, about 40% to 50% of individuals who suffer from an illness do not have a diagnosis. According to different surveys, the average delay in diagnosis is 7 to 8 years. Some will eventually get their diagnosis, but others may not get one in their lifetime. However, today, the new technologies in genomics allow a more rapid identification of known genetic diseases and even the characterization of “new” diseases.
Further reading: International Recommendations to Address Specific Needs of Undiagnosed Rare Disease Patients
Swan UK (Syndromes Without a Name UK)
Approximately 3,000,000 Canadians are affected by a rare disease
There is no accurate count of the number of people with rare diseases in Canada. The Canadian Organization of Rare Disorders (CORD) estimates that one in 12 people (1/12) in the Canadian population is affected, representing approximately 3,000,000 people.
More than 300,000,000 people are affected by a rare disease worldwide. Further reading: Rare Diseases International
Nearly 75% of these diseases affect children
Rare diseases can appear at any time in life: from conception, during in utero life, after birth, during childhood, adolescence or adulthood. Almost 75% of these diseases affect children and 30% of them die before the age of 5 years.
80% of rare diseases are of genetic origin
About 80% of rare diseases have a genetic cause. Other types of rare diseases include cancers, autoimmune or inflammatory diseases, infections, poisonings, etc.
Rare diseases are very diverse in their presentation: acute diseases, chronic diseases, complex syndromes with or without malformations, diseases with progressive evolution, severe and fatal diseases, recurrent or episodic diseases, unpredictable diseases, diseases with physical disabilities, diseases with intellectual disabilities, diseases with physical and intellectual disabilities, diseases with “invisible” disabilities (e.g., immunodeficiency, pain, fatigue) and conditions affecting physical appearance.
What is an orphan disease?
The term “orphan” appeared in the early 1980s in the United States in connection with the treatment of rare diseases. Thus, a disease was said to be orphan if there was no treatment for the disease other than treating the symptoms. Companies or researchers were reluctant to develop a drug for a rare disease because it was not financially profitable.
Only about 5% of rare diseases have a specific treatment
In 1983, the United States introduced the Orphan Drug Act. Forty years after its application, the Food and Drug Administration estimated that it had approved drugs for only about 5% of rare diseases (A comprehensive study of the rare diseases and conditions targeted by orphan drug designations and approvals over the forty years of the Orphan Drug Act, 2023).
The good news is that there is an increased interest in rare diseases and there are thousands of new drugs in development. Many are innovative therapies: for example, cell and gene therapies.
The term “orphan disease” has been generalized and often the terms “rare disease” and “orphan disease” are used indiscriminately, because the vast majority of rare diseases are orphan diseases in many ways: lack of knowledge about the disease, difficulty in diagnosing it, little information on medical care, little or no research and no treatment.
We can say that many rare diseases are orphan diseases, because they are little known by the population and the medical community, they are the subject of little research and they result in a feeling of being left behind by the person who are affected and by their family.
A rare disease may be orphan in terms of diagnosis, research, treatment, care, etc. Those who suffer from a rare disease often feel alone.
Why is the zebra the mascot of rare diseases?
The zebra became the symbol of rare diseases because of the expression coined in the 1940s by Dr Theodore Woodward, professor at the University of Maryland School of Medicine, who instructed his medical students: “When you hear hoofbeats behind you, don’t expect to see a zebra.” Since zebras are much rarer than horses, the sound of hoofbeats would almost certainly be from a horse (a common disease). Dr. Woodward wanted to convey to his students that when they are searching for a diagnosis, they should think of a horse first, not a zebra. He believed that doctors in training had a predisposition to remembering rare diseases that they had encountered.
However, patients have suffered from long delays in diagnosis because many doctors do not have the reflex or the knowledge to look for the rare, the zebras.
For doctors: #DareToThinkRare See Medics4RareDiseases