Rare diseases are more common than you might think

More than 300 million people worldwide live with rare diseases, for which there are no preventative measures, no cures, and no effective treatments.

There are about 7,000 different rare diseases. Each year, Rare Disease Day – which falls this year on 29 February – raises awareness of these conditions. Some are debilitating and some are life-threatening; one-in-three children born with a rare disease will die before they reach the age of five.

Examples of rare diseases include cystic fibrosis, muscular dystrophy, spina bifida, haemophilia, amyotrophic lateral sclerosis, porphyria, sickle cell disease, and Huntington’s disease. Many are genetic conditions, some are triggered by infections, allergies or have environmental causes.

According to the European Commission, if a condition affects fewer than five people out of 10,000 it is classed as rare. In the US, the term is used for any illness with less than 200,000 sufferers. It also includes the prevalence of conditions such as arthritis in children; although commonly experienced in many older adults, arthritis affects approximately 12,000 children in the UK.

Here are three examples of better-known rare diseases.

Amyotrophic lateral sclerosis

ALS is also known as motor neuron disease and in the US by the name Lou Gehrig's disease. Gehrig was a professional baseball player diagnosed with ALS in 1939, although when his symptoms first appeared, doctors told him he had a problem with his gallbladder. It brought his unbroken streak of 2,130 games to an end. He died two years later.

People with ALS experience a gradual degeneration and eventually the death of their motor neurons. These are the nerve cells that connect the brain and the voluntary muscles – those involved in walking, talking, chewing. As the muscles begin to weaken, people with ALS gradually lose their strength – not only are they unable to speak, eat, or move, but eventually even breathing is not possible.

Stephen Hawking, the eminent mathematician, theoretical physicist and cosmologist, also suffered from the disease. He was diagnosed with the condition in 1963 at the age of 21 but unlike most people with ALS, Hawking lived for another 55 years.

Sickle cell disease

Sickle cell disease is an inherited condition that affects the molecule in red blood cells that delivers oxygen around the body – haemoglobin. Red blood cells are distorted into a crescent or sickle shape. It is particularly common in people from African or Caribbean families.

When red blood cells become sickle-shaped they break down, leading to anaemia, which in turn can trigger a range of symptoms: shortness of breath, tiredness, delayed growth and development in children, repeated infections, and periodic episodes of pain.

The pain is caused by the misshaped red blood cells becoming stuck in small blood vessels. When that happens, tissues and organs are starved of oxygen-rich blood. In serious cases, this can lead to organ damage, especially in the lungs, kidneys, spleen, and brain. Sickle cell disease can also cause abnormally high blood pressure in the vessels that supply the lungs with blood. Around one-third of adults with the disease will experience this and some will go on to suffer heart failure as a result of it.

Huntington’s disease

Huntington's disease is sometimes known as Huntington's chorea. Like sickle cell disease, it is an inherited degenerative illness. It causes a progressive breakdown of nerve cells in the brain, most notably leading to movement-related challenges. It also damages a person’s cognitive abilities and can cause psychiatric disorders.

The disease was named after an American doctor, George Huntington, who catalogued its symptoms and effects in 1872.

Huntington's is caused by an inherited defect in a single gene. A parent with this defect could pass along the faulty or the healthy copy of the gene to their children. That means the child of a parent with that gene defect has a 50:50 chance of inheriting the gene that causes Huntington's.

The disease can linger for up to 30 gruelling years. The list of symptoms they are likely to experience is both long and distressing, it includes:

Involuntary jerking movements and muscle problems

Difficulty speaking or swallowing

Lack of impulse control that can result in outbursts

Slowness in processing thoughts or ''finding'' words

Feelings of irritability, sadness or apathy

It is common for people with Huntington's to die as a result of pneumonia and infections, fall-related injuries, or complications caused by not being able to swallow.

Diagnostic delays

One of the challenges facing people with a rare disease can be getting an accurate diagnosis and it is not unusual for a sufferer to be misdiagnosed initially. The less common a particular illness is, the less likely it is that a family doctor or GP will have encountered it before and the fewer points of reference they will have to draw upon. That potential lack of personal contact between an individual clinician and rare diseases can be overcome by better access to data, potentially connecting doctors around the world.

The search for treatments and cures for rare diseases draws heavily upon genetic research, seeking to find the connections between genes and particular conditions. Being able to connect researchers around the world with each other’s data and insights could help accelerate the discovery of life-changing medical treatments.

The Global Alliance for Genomics and Health (GA4GH) is working to establish common frameworks of standards that govern the sharing of research and patient data worldwide. It is made up of academics, research scientists, clinicians, government agencies and private businesses, creating technical standards and policies to ensure sensitive information is used responsibly.

The World Economic Forum is also working on initiatives to foster the development of frameworks that have consistent patient consent processes and data security protocols so the insights gleaned from such data can be used to rapidly diagnose diseases and define tailored treatments that improve the quality of patients’ lives.