What is a Rare Disease?

In the United States, the National Institutes of Health (NIH) defines a rare disease as a condition that affects fewer than 200,000 people. Rare diseases may include many single gene disorders, childhood and adult diseases, and some childhood cancers and infectious diseases. They also include the diseases on state newborn screening tests.

Rare diseases can cause long-term illness, physical and intellectual disabilities, and reduced lifespan. Some individuals and families affected by rare diseases face challenges related to the financial cost of medical management and treatment. Also, many rare disease patients and families, especially those who are newly diagnosed, may feel overwhelmed when searching for information and resources related to their disease.

What causes Rare Diseases?

Rare diseases have many different causes, although a high percentage are thought to be genetic. A genetic disease is directly caused by a change to a gene or chromosome. Genetic changes that cause disease are sometimes called mutations or genetic variants. These genetic changes are often passed from one generation to the next. This is known as an inherited genetic variant.

In other cases, the genetic change occurs randomly in a person who is the first in a family to be diagnosed; this is called a spontaneous mutation. Many rare diseases do not have a known genetic cause. These include infections, some rare cancers, and some autoimmune diseases. Researchers continue to learn more about rare diseases each year, although the cause of many rare diseases is unknown.

What is the prevalence of Rare Diseases in the U.S. and in Alabama?

Although individual diseases may be rare, it is estimated that there are more than 7,000 rare diseases that affect 25 to 30 million Americans. One out every 10 Americans lives with a rare disease.

In Alabama, about 400,000 residents are affected by rare diseases. This number translates to about 8.2% of the state’s population that is living with a rare disease.

These numbers are only estimates, however. This is because only a few types of rare diseases are tracked in the U.S. Because most rare diseases are not tracked, it can be difficult to determine the exact number of rare diseases and how many people are affected.