Rare Diseases 101

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January 15, 2025

February 28, 2025 is Rare Disease Day.

By definition, “rare” means uncommon. Unusual. Words you typically don’t think of when you’re thinking about your health.

But living with a rare disease is a reality for a lot of people. Rare diseases affect 400 million people worldwide and 30 million people in the U.S. That means about 1 in 10 Americans are living with a rare disease.

You’ve probably heard of some of the more well-known examples, such as cystic fibrosis and sickle cell disease. But there are more than 10,000 rare diseases with more being recognized each day. Some affect as few as a handful of people across the world.

The path to a diagnosis and treatment is often long and complicated for people living with a rare disease. “[A diagnosis] currently takes four to six years on average with thousands of patients annually that remain undiagnosed,” said Nicole Boice, founder and chief mission officer of Global Genes/RARE-X, a nonprofit organization dedicated to helping people with rare diseases.

The complexity of the condition and lack of known history can cause delays in getting the right diagnosis and, in many cases, the disease is so rare that treatment options may not even exist. In the U.S., only 5% of rare diseases have an FDA-approved drug for treatment.

Today, there are more than 10,000 known types of rare diseases. About half of the people with rare diseases are children — and women are often the caregivers in charge of navigating through the unknown waters. “Over 80% of those we serve at Global Genes identify as women, mothers and caregivers,” Boice said.

Researchers predict more people will be diagnosed with rare conditions as genetic testing becomes more accessible and the knowledge of rare diseases continues to expand.

Here’s what you need to know if you or someone you know is living with a rare disease.

What is a rare disease?

A rare disease is determined by how many people are affected by the disease, and the definition can vary by country. In the U.S., a condition is considered rare if it affects less than 200,000 people.

What are the challenges to getting diagnosed with a rare disease?

On average, a person with a rare disease will see more than 10 specialists and have three misdiagnoses before getting the right diagnosis. These delays can happen for a number of reasons.

A diagnosis can be tricky because the symptoms of the rare disease may look different from person to person. Symptoms can also look like other conditions, people can have several symptoms that seem unrelated or can have an unusual presentation of a known rare disease. Usually, rare diseases are diagnosed by exclusion, meaning more common diseases are ruled out while trying to determine a diagnosis.

In many cases, the delay in diagnosis happens because healthcare providers (HCPs) don’t have knowledge or experience with the disease because they don’t see it very often or have possibly never seen it or even heard of it. “Clinically, doctors are taught to look for common diseases when patients are facing challenges, [so] they spend a lot of time looking for and testing for everything that is common,” Boice said.

There are unique challenges for children with rare diseases, including limited time to receive diagnosis and treatment and few clinical trials available. As primary caretakers of these children with rare diseases. Because of these challenges, most rare diseases require a referral to a specialist and the wait times to see specialists are often long. To make matters more complicated, many rare diseases impact multiple organ systems and are treated by more than one specialist.

Testing for rare diseases can be challenging. For example, common diseases like diabetes or hypertension have several go-to tests that can lead to a quick diagnosis. But 8 out of 10 rare diseases are caused by faulty genes and are diagnosed through a combination of tests, including genetic testing which is more complex than a routine blood test. And the results may still not be enough for a diagnosis.

Cost and access to resources can also be roadblocks on the way to a diagnosis. For example, testing may not be covered by health insurance, which can mean huge out-of-pocket costs for the person with the rare disease. Finding the right specialist may also require traveling or relocating to another place for testing and treatment.

Why are treatments for rare diseases difficult to develop?

Treatments for rare diseases can be difficult to develop. For one, less people means a smaller recruiting pool for clinical trials and research that’s needed to understand the disease and move forward with treatment possibilities.

Then there’s the cost. The complex makeup of rare diseases and the different ways they present make it difficult and expensive to design research studies for drug development.

About half of rare diseases don’t have a specific foundation or research group that helps advocate for funding and support. So, these conditions are often overlooked and left behind regarding treatment options.

The importance of education, advocacy and policies for rare diseases

Because there often isn’t a strong incentive for pharmaceutical companies to fund research on rare diseases, many of the new research efforts are driven by people living with the rare disease and their communities.

Patient advocacy groups like Global Genes, the National Organization for Rare Disorders and the EveryLife Foundation for Rare Diseases play a big part in driving policy that creates support for research and advancements for rare diseases. “They can de-risk future investment by manufacturers, and get the research to a point where it becomes attractive to investors and others that develop therapies.”

Without people advocating for rare diseases, legislators probably won’t support policies to help find treatments and cures. But advocacy efforts that help put the spotlight on rare diseases can make policymakers and legislators aware of the challenges, including lack of medical advancements and equality in healthcare. “Legislative advocacy plays an important role in driving innovation and enabling faster diagnosis, better clinical care, innovations in research and science, and driving more impactful therapies,” Boise said.

There is some legislation in the works that offers hope regarding rare diseases: For example, in March, the SEARCH Act was proposed to help fund new efforts to increase the number of women in clinical research trials for rare diseases and blood disorders.

And in May, several bipartisan bills important to the rare disease community advanced in the House, including the RARE Act ensuring incentives to spur rare disease research and developing for life-saving drugs and the Telehealth Modernization Act, which would extend telehealth access to reduce barriers to care for many rare disease patients.

Advocacy groups also help connect people living with rare diseases and their families to resources and support. Umbrella organizations, like those mentioned above, provide updated and curated educational content for newly diagnosed families, as well as connections to smaller reputable patient organizations with content specific to thousands of rare diseases. The sense of community that these organizations provide can be vital for people who feel alone or are unsure how to move forward after a diagnosis. This is especially important considering that treatment options are in short supply and general information on the web is often outdated and scary.

Are there barriers specific to women living with rare diseases?

Similar to what we see with many other health conditions, research shows women are more likely to receive a delay in diagnosis for a rare disease compared to men. This may be in part due to the fact that women are more likely to have their symptoms dismissed or not believed by HCPs compared to men.

Also, historically, women have been left out of clinical trials and research, which has led to delays and poorer outcomes for women.

On the caregiving side, Boise said women are usually the ones to stay home to support the medical needs of the person with the rare disease. And the support doesn’t stop there. “Women have to be tenacious, move mountains, be creative and become experts in the disease, often knowing more than the physicians,” she said.