Rare Disease Statistics

Reviewed by: HU Medical Review Board | Last reviewed: September 2022 | Last updated: November 2023

There are between about 5,000 and 10,000 conditions that are called rare. The US Rare Diseases Act of 2002 defined a rare condition as one that affects "small patient populations, typically populations smaller than 200,000" people. This is about 1 in 10 Americans.1-5

The European Union defines a rare condition as one that “affects no more than 1 in 2000 people.” Examples of these conditions include:3,6-10

The "rare" label covers many different types of conditions. The majority of rare conditions are genetic disorders. There are also many that are the result of outside factors, such as infectious diseases. And some are special forms of cancer.5,11,12

Who is likely to have a rare condition?

Rare conditions are defined as affecting a very low portion of the general population. They can still be common in smaller specific groups.

For example, rare conditions affect children at much higher rates:5,12,13

  • About 50 percent of people with a rare condition are children.
  • About 35 percent of children with a rare condition will die before turning 1 year old.
  • As many as 30 percent of cases of rare conditions in children may be fatal by age 5.

There are also instances of rare conditions that are more common in some racial or ethnic groups:8,9,14-16

  • Sickle cell disease is considered a rare condition. But it has historically affected Black people at a higher rate than others. In the United States there are an estimated 73 cases of sickle cell trait in 1,000 among Black newborns. For white newborns, there are 3 cases in 1,000.
  • Tay-Sachs disease is another rare condition. But it can be commonly found in Ashkenazic (eastern European) Jewish populations. In people of Ashkenazi Jewish descent, 1 in 25 carry the mutation that causes Tay-Sachs disease.

These trends can serve as a guide to knowing if you should get checked for a specific condition. Family history of a condition can also serve as an indicator of risk.

Treatment and tests for rare conditions

It is hard to study rare conditions when such low numbers of people are affected. The way rare conditions behave (genetic origins, rare pathogens) complicates creating tests and treatments. The complex nature of tests and treatments often affects costs.

Genetic testing technology has made it easier to find risk early on. Sometimes, knowing your level of risk can go far in helping you manage your condition. Whole genome sequencing is a type of genetic test used to diagnose a condition. These tests can cost several thousand dollars in some cases.17

Treatments for rare conditions can include drugs, procedures, or medical devices. Many treatments are difficult to make and can be expensive. For example, therapies for spinal muscular atrophy (SMA) can range from a few thousand dollars to hundreds of thousands of dollars. Costs depend on the type of SMA and the country where the therapy is delivered.1,18

If you are concerned about a family history of specific conditions, talk to your doctor. You should also talk to your doctor if you are concerned with treatment options or financial help for treatment. There are many organizations dedicated to rare conditions in general. For example, you can visit Rare Diseases International for more information.

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