Diagnosis and treatment of rare genetic diseases

DOI: https://doi.org/10.58248/PN763

Rare diseases are those that affect fewer than 1 in 2,000 people. Collectively, they affect around 3.5 million people in the UK.

Around 80% of rare diseases have a genetic cause, and most begin in childhood.

Over 7,000 rare genetic diseases have been identified, and around 95% have no effective treatment. Some patients never receive a diagnosis.

The average time to diagnosis is estimated at four to six years, often involving multiple appointments across different medical specialties.

The Medicines and Healthcare products Regulatory Agency (MHRA) have said that “the cost of delayed diagnosis and limited treatment options [for rare diseases] is estimated at £340 million annually, with a further £4.7 billion in health-related disability costs and a £14.9 billion annual loss to the economy”.

Frameworks, strategies and policies

The 2021 UK Rare Diseases Framework sets priorities to speed up diagnosis, improve awareness among healthcare professionals, coordinate care more effectively and improve access to specialist services.

deliver the Framework through separate annual action plans. The 2026 England Rare Diseases Action Plan aligned with the 2025 NHS 10 Year Health Plan.

Screening and diagnosis

Screening identifies whether a person has an increased risk of a disease, whereas diagnostic testing confirms or rules out a specific condition.

Newborn screening in the NHS uses the Newborn Blood Spot (NBS) test, which screens for 10 rare diseases.

The UK screens for fewer conditions than some other countries. In early 2026 there was parliamentary, public and media interest in adding spinal muscular atrophy (SMA) to England’s NBS, and Scotland launched a SMA screening pilot in March 2026.

The Generation Study will assess whole genome sequencing (WGS) as a screening tool for over 200 genetic diseases. Ethical considerations include consent, data governance and the potential for overdiagnosis.

Treatment

Treatments include commonly prescribed medicines, specialist diets and advanced therapy medicinal products (ATMPs). ATMPs include gene therapies, cell therapies and tissue-engineered products.

Some gene therapies can provide long-term symptom alleviation after a single dose, as seen in treatments for SMA. Regulatory and industry bodies say that assessing ATMPs can be challenging because of small patient populations, high upfront costs and long-term uncertainties.

Coordinating care and inequalities

Patients often require support from multiple specialists across different locations. Research shows variation in access to specialist centres and care coordinators.

Some researchers and charities also identify inequities linked to ethnicity, socioeconomic status and place of residence. Some minority ethnic groups are underrepresented in genomic datasets, reducing the accuracy of some genetic tests.

Data initiatives aim to improve understanding of rare disease prevalence, diagnostic timelines and outcomes.

Acknowledgements

This briefing was produced in consultation with experts and stakeholders, who are listed at the end of the briefing. The briefing was co-funded by Midlands Innovation. POST would like to thank everyone who contributed their expertise to this briefing.