What are rare diseases?

A rare disease is a disease that affects a small percentage of the population but there is no single accepted definition. 

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 a study 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 data estimates 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.

What are examples of rare diseases?

For a comprehensive list of the known rare diseases, please see the following databases:

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 the National 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.

What are the different effects of rare diseases?

To illustrate how diverse rare conditions are in their symptoms, cause and impact, we’ve compared a few examples below.

Some are genetic, while others have no genetic cause…

Duchenne Muscular Dystrophy (DMD) is a genetic condition caused by a mutation in the dystrophin gene.

Affects: 1 in 3,500 boys worldwide

While Guillain-Barré syndrome (GBS) is often triggered by an infection.

Affects: 1-2 in 100,000

Some genetic conditions are inherited, while others arise from new changes to the genes…

Friedreich’s ataxia is a condition that is inherited from your parents.

Affects: 1 in 30,000 Caucasian people

While Fibrodysplasia ossificans progressiva (FOP) is caused by a spontaneous mutation early in the development of an embryo.

Affects: 1 in a million people

Some affect you later in life, while others affect you from birth…

Symptoms of Alkaptonuria (AKU) only really develop in early middle age.

Affects: 1 in every 250,000 people worldwide

While Spinal Muscular Atrophy (SMA) effects children from birth.

Affects: At least 1 in every 100,000 people worldwide have a Type of SMA

Some affect a particular body system, while others can cause cancer…

Tay-Sachs disease leads to neuro degeneration from a young age.

Affects: 1 in 320,000 people

While Pseudomyxoma Peritonei (PMP) is a rare cancer of the appendix.

Affects: 2 people per 1 million each year

Some are visible, while others are hidden from sight…

Achondroplasia, otherwise known as dwarfism, is immediately visible to other people.

Affects: 1 in every 40,000 people

While Vascular EDS causes a weakness in the walls of the arteries, but no symptoms can be seen by others.

Affects: 1 in 90,000 people

Some have ways to treat the underlying condition, while others have treatments for a symptom…

Tuberous Sclerosis Complex has treatments to reduce a range of tumours that occur.

Affects: 1 million people worldwide

While Tyrosinemia Type 1 can be completely prevented with a single drug.

Affects: 1 in 100,000 individuals worldwide

What are the most common rare diseases? 

Some of the most well-known rare diseases are:

  • Ehlers –Danlos Syndrome (EDS)
  • Sickle Cell
  • Cystic Fibrosis
  • Duchenne Muscular Dystrophy (DMD)
  • Haemophilia

You have probably heard about these in the media or know someone who has been affected by the disease. These diseases are in fact rare, but they receive the most awareness, funding and research in comparison to very rare and ultra-rare diseases.

Rare conditions are all around you. You just may have never known!

How many rare diseases have treatment?

There isn’t a consensus on how many rare diseases have treatment. Because the number is so hard to pinpoint, rare disease stakeholders say that roughly 95% of rare conditions do not have a treatment. This means that only 5% of rare conditions have a licensed treatment.

At Beacon, we are working to change this. We believe that the key to advancing rare disease treatment is through drug repurposing.

What rare diseases all have in common

There is a common thread that connects all rare disease patients and families. Medical understanding, knowledge and research of rare diseases are limited. Patients and their families often fall victim to misdiagnosis, delayed treatment, poor care coordination and a lack of support. Having a rare disease can be an isolating experience not only for the patient, but also his or her family. Rare conditions and those they affect should not be overlooked by doctors and researchers.

At Beacon, we want to see the day when no one is handed a Google printout and is simply told to go home and deal with it.

Regardless of which rare medical condition a person has, the following remains true:

The average rare disease patient waits 4 years before they receive their final diagnosis

The average rare disease patient consults with 5 doctors and receives 3 misdiagnoses

One third of rare disease patients do not have access to the medicine they need

One third of rare disease patients only have access to a treatment after waiting years

Treatments that do exist often cost 7x the price of those developed for a common condition

2 in 3 patients and carers struggle to hold paid employment

Source: Rare disease statistics based on data collected by Rare Disease UK


How can Beacon help you

Click on the link which best describes you. We’ll point you to our most relevant pages and additional places for support within the rare disease community.