The European Union and United Kingdom define a disease as rare if it affects fewer than 1 in 2,000 people, but there is no universal definition. Each country has its own definition of how prevalent rare diseases are amongst its population. What we do know is that rare conditions can evade detection for years.
Rare diseases present a wide variety of symptoms, which often appear unrelated on the surface. Rare medical conditions can touch a person’s life at any moment; during childhood, adulthood or both. Rare disorders, as they are sometimes called, can affect a single system in the body or multiple organs. Rare disease symptoms and their impact on patients are as diverse as the diseases themselves.
How many rare diseases are there in the world?
According to astudy on rare diseases published by Wakap et al. (2020), there are 6,172 unique rare diseases. Of the 6,172 unique rare diseases, Wakap et al. (2020) found that:
- 69.9% (3,510 rare diseases)are exclusively paediatric onset
- 11.9% (600 rare diseases) are exclusively adult onset
- 18.2% (908 rare diseases) have onset spanning both paediatric and adult groups
The RARECARE European population-based rare cancer registry dataestimates that 4,300,000 people are living with a rare cancer diagnosis in the European Union alone. This accounts for 24% of all cancer diagnoses in the EU.
Global rare disease prevalence: they are more common than you think!
Globally, rare diseases affect between 3.5% and 5.9% of the population. This means that anywhere between 263 million and 446 million people are living with a rare disease in the world. Wakap et al. (2020).
Go around the world to discover the most up-to-date definitions of how many people are affected by rare disease in each country.
Africa definition
Affects fewer than 1 in 2,000
China definition
Affects fewer than 1 in 1,316
Brazil definition
Affects fewer than 65 out of 100,000 individuals (1 in 1,538 people)
America definition
Affects fewer than 1 in 1,250 people
Rare cancers in the EU
Affects fewer than 108 in 100,000
Canada definition
Affects 1 in 12 Canadians. Approximately 3 million Canadians and their families have a rare disease.
What are examples of rare diseases?
For a comprehensive list of the known rare diseases, please see the following databases:
- Orphanet Database for Rare Diseases and Orphan Drugs
- National Organization for Rare Disorders (NORD) Rare Disease Database
Rare diseases are classified and understood as either genetic or non-genetic in nature. If a rare condition is not genetic in nature, then the cause will be environmental in some way.
The condition could have been triggered by a bacterial or viral infection, an allergen or other environmental factors, such as breathing in asbestos. Some rare medical conditions remain unexplained.
What is a genetic condition?
A genetic condition is one that is caused by an error or mutation in a person’s DNA. The errors in a person’s genes cause proteins to be built incorrectly. When the proteins are built incorrectly, a change in the way the body functions results. This change causes the symptoms of a rare disease.
A genetic disorder, as it is sometimes referred to, can be caused in the following four ways, according to theNational Human Genome Research Institute:
- A mutation on one gene (Monogenic)
- A mutation on multiple genes (Multifactorial inheritance)
- A combination of gene mutations and environmental factors
- Structural damage to chromosomes
Most genetic conditions are heritable, which means that they have been passed down from parents to their children. Some genetic conditions are caused by completely new mutations that arise in an individual. These are called spontaneous mutations, which can occur in an egg, sperm or developing embryo.
Did you know?
72% of all rare diseases are genetic in nature, of which 80% are inherited.
