Introduction to rare disease

Although rare diseases are individually rare, they are collectively common. Over 7,000 rare diseases have been recorded, affecting 3.5 million people in the UK, 30 million people across Europe, and 300 million people worldwide. In the UK it is estimated that 1 in 17 people will be affected by a rare condition at some point in their lives.

Because it is impossible for a healthcare professional to receive training in every rare disease, it is important to be aware of rare diseases more generally. This means recognising the signs of rare disease in a patient and being aware of how to make a referral to a specialist for potential diagnosis, treatment and support. Just like in other areas of medicine such as cancer, people with rare conditions need care plans, medication reviews, mental health reviews, family planning advice and an overview of research opportunities. Ultimately, every patient deserves care, no matter how rare their condition may be.

Because about 80% of rare diseases are thought to have a genetic origin, genomics – the study of an individual’s complete genetic information – is being increasingly recognised for its potential to help people with rare diseases.

About 70% of rare diseases present exclusively in children, and more than 30% of children with a rare disease die before their fifth birthday. Newborn screening is used to test for some rare conditions, to help prevent severe disability or even death. However, there are significant disparities between countries in the number and types of diseases that are tested for in national newborn screening programmes. For example, the UK tests for nine rare conditions, while Italy screens for more than 45. This is why newborn screening was made a priority in the England Rare Diseases Action Plan 2023, as part of the drive to help patients receive a faster diagnosis.

Watch this short video to hear Beskida and Arvin’s story about the impact a genetic diagnosis can have on a family living with a rare condition.

We can categorise rare diseases into four broad types: single gene, chromosomal, multifactorial and non-genomic. While many rare diseases are caused by variants in a person’s genes (which may be inherited or may have arisen for the first time (de novo) in that person), others are caused by factors such as disordered immunity or infections. It is important not to overlook the 20% of rare diseases that are non-genomic.

People living with rare diseases and their families are often faced with a variety of challenges when it comes to healthcare. The rarity of a person’s condition can mean that little is known about it, which can lead to a lack of understanding and support. In addition, rare conditions are often complex, affecting multiple body systems, and require coordinated care. This can all have a profound impact on the lives of rare disease patients, affecting factors such as access to education, financial stability and mental health.

Most people with a rare condition will face what is known as the ‘diagnostic odyssey’: a term used to describe the long journey to a diagnosis, often being passed between numerous healthcare professionals in numerous specialties. Even if an accurate diagnosis is reached, the journey usually doesn’t end for the patient: there is often a lack of treatment options, limited awareness of their condition and scant support available.

Because little is known about many rare diseases, patients often become the ‘experts’ in their own condition. Most people they meet, including healthcare professionals, will know little or even nothing about their condition; this means that they and their families and/or carers frequently bear the burden of explanation. While it can be helpful for healthcare professionals to hear from a patient about how their rare condition affects them, having to repeat this information on a regular basis can be exhausting for the patient themselves.

Rare diseases often affect multiple body systems, requiring multi-specialist input. Most do not have specific treatments or cures and therefore require access to multiple specialist therapies, such as speech and language therapy and physiotherapy. This can affect the patient’s life and the lives of their family members and/or carers in a number of different ways: for example, the centres providing these therapies may not be located close to the patient’s home, requiring them to travel long distances for appointments and impacting their time and financial circumstances.

There is always something that can be done to help support patients and their families, even if a disease-specific treatment is not an option.

A good place to signpost rare disease patients to is an appropriate patient advocacy group. These can be disease-specific or umbrella groups, and they exist to provide information, resources and community support for patients and families. A good example is SWAN UK, the patient advisory group that supports people who have a ‘syndrome without a name’ (SWAN), which means that they remain undiagnosed. Effective treatment, management and coordination of care, combined with support from patient groups, can significantly improve the lives of patients and their families.

Another important way in which you can support your patient is by keeping them informed about any ongoing research and/or clinical trials. Due to the general lack of treatments for rare conditions, many patients are keen to be involved in research that aims to identify a cause for their condition and develop treatments.

For clinicians

• Department of Health and Social Care: England Rare Diseases Action Plan 2023: Main report
• Medics4RareDiseases: Available courses
• Rare 2030: The Rare 2030 recommendations
• Rare Diseases International: Operational description of rare diseases
• Technology Networks Diagnostics: A landscape assessment of newborn screening in Europe

For patients

• EURORDIS: Living with a rare disease
• SWAN UK