When taken cumulatively, rare diseases still affect a substantial proportion of the population.

In the USA and the UK, some 1 in 15 to 1 to 20 people suffer from a rare disease, although definitions of what constitutes a rare disease differ.

For instance, in the US, the Rare Diseases Act of 2002 defines a rare disease as affecting fewer than 200,000 people, whereas in the EU, the European Commission has a different benchmark, defining diseases as rare when they affect more than 1 in 2,000 people.

So, what causes rare diseases, and how are they treated?

What Causes Rare Diseases?

Rare diseases have numerous genetic, environmental, idiopathic and unknown causes. In some cases, they originally stem from genetic mutations, which are later activated by environmental triggers.

Here’s a deeper exploration of how rare diseases are caused or triggered:

Genetic Factors

Genetic factors are the primary cause of many rare diseases. These diseases are often inherited and emerge when specific genes mutate, disrupting bodily functions or causing developmental issues.

Sometimes, long-term genetic risk factors are ‘activated’ by short-term triggers.

• Cystic Fibrosis: Related to mutations in the CFTR gene, this disease primarily affects the respiratory and digestive systems by producing thickened mucus. It’s passed on through a recessive inheritance pattern.
• Huntington’s Disease: A neurodegenerative condition, Huntingdon’s is attributed to mutations in the HTT gene. Children have a 50% chance of inheriting the disease if one parent has the mutated gene.
• Phenylketonuria (PKU): Affecting fewer than 1 in 10,000 babies, PKU derives from mutations in the PAH gene, leading to an impaired ability to break down amino acids.

Environmental Triggers

While genetics often play a role in rare disease development, environmental triggers can exacerbate or initiate their onset. Environmental triggers play a crucial yet mysterious role in the development of numerous more common and rare diseases.

Here are some known cases:

• Porphyria: Although having a genetic foundation, this disease group also reacts strongly to environmental triggers. Exposure to drugs, stress, sun, or certain foods can lead to an acute attack.
• Lupus: Affecting between 2 and 8 people per 100,000, Lupus has an underlying genetic risk, but external factors can instigate or worsen the disease. Sunlight, infections, and specific medications are known triggers.
• Paraneoplastic Pemphigus: While associated with cancers, trauma or specific

Unknown Causes

In some cases, rare diseases have no widely agreed root cause. They often have multifactorial origins that vary from patient to patient.

Rare diseases with poorly understood or unknown causes include:

• Reflex Sympathetic Dystrophy (RSD): A rare disease that causes chronic burning pain, the exact origins of RSD remain unknown. Injuries or surgical procedures can sometimes lead to its onset.
• Stiff Person Syndrome: Predominantly marked by muscle rigidity and spasms, this exceptionally rare disease – considered one of the rarest worldwide – is likely immune-system related.
• Chronic Fatigue Syndrome (CFS): CFS, though still considered rare, has become more common in recent times. It’s often associated with infection, but a conclusive cause has not been identified.

How Many Rare Diseases Have Treatments?

Current estimates suggest there are between 6,000 to 8,000 rare diseases known to science.

Merely 5% of these diseases have recognised treatments. If a rare disease has a single known treatment, this is called an “orphan treatment.” A significant majority of rare disease sufferers, along with their healthcare providers, are faced with conditions that currently lack concrete therapeutic pathways. Again, while the incidence rate of each rare disease is low, the cumulative impact is high, affecting some 1 in 15 people on average.

Developing treatments for these diseases presents a distinctive set of challenges. Given the small number of individuals diagnosed with any specific rare disease, conducting comprehensive clinical trials is problematic. Additionally, raising funding for rare disease research is also tricky. Funding for rare disease research has generally increased, with 2023 heralding a significant £14m investment from the Medical Research Council (MRC) and the National Institute for Health and Care Research (NIHR) in the UK.

Improving Rare Disease Medication Accessibility With Masters

While rare disease sufferers often face challenging journeys, there is hope.

The increased focus on research, development, and accessibility of treatments is paving the way for a brighter future. More doctors and clinicians are dedicating their research to rare diseases, increasing the availability of effective and novel treatments.

Masters are a global pharmaceutical company that recognises the challenges associated with rare diseases and is committed to increasing accessibility to their medications. We are expert pharmaceutical drug suppliers making medicines available in emerging markets extends to rare diseases. We continually strive to transform lives through the power of medication.