A rare disease is any disease that affects a small percentage of the population. In the United States, a rare disease is defined as an illness that affects fewer than 200,000 people. The prevalence of a rare disease usually is an estimate and changes over time.
Rare diseases affect 1 in 10 Americans. Over 30 million people in the United States, and 350 million people in the world have a rare disease. According to the U.S. Department of Health and Human Services and the National Institutes of Health, there are about 7,000 rare diseases and about 95% of all rare diseases do not have a single FDA approved drug treatment. There are less than 500 treatments approved by the FDA for the nearly 7000 rare diseases which have been identified.
Most rare diseases are genetic, and thus are present throughout the person’s entire life, even if symptoms do not immediately appear. Many rare diseases appear early in life, and about 30% of children with rare diseases will die before reaching their fifth birthday.
In the United States, the Rare Diseases Act of 2002 defines rare disease strictly according to prevalence, specifically “any disease or condition that affects fewer than 200,000 people in the United States”, or about 1 in 1,500 people. This definition is essentially like that of the Orphan Drug Act of 1983, a federal law that was written to encourage research into rare diseases and possible cures.
However, the European Commission on Public Health defines rare diseases as “life-threatening or chronically debilitating diseases which are of such low prevalence that special combined efforts are needed to address them.” The term low prevalence is later defined as generally meaning fewer than 1 in 2,000 people. Diseases that are statistically rare, but not also life-threatening, chronically debilitating, or inadequately treated, are excluded from their definition.
Because of definitions that include reference to treatment availability, a lack of resources, and severity of the disease, the term orphan disease is used as a synonym for rare disease. But in the United States and the European Union, “orphan diseases” have a distinct legal meaning. The orphan drug movement began in the United States.
The United States’ Orphan Drug Act includes both rare diseases and any non-rare diseases “for which there is no reasonable expectation that the cost of developing and making available in the United States a drug for such disease or condition will [be] recovered from sales in the United States of such drug” as orphan diseases.
The European Organization for Rare Diseases (EURORDIS) estimates that as many as 5,000 to 7,000 distinct rare diseases exist, and as much as 6% to 8% of the population of the European Union is affected by one. Only about 400 rare diseases have therapies and about 80% have a genetic component according to Rare Genomics Institute.
Rare diseases can vary in prevalence between populations, so a disease that is rare in some populations may be common in others. This is especially true of genetic diseases and infectious diseases. An example is cystic fibrosis, a genetic disease: it is rare in most parts of Asia but relatively common in Europe and in populations of European descent. Many infectious diseases are prevalent in a given geographic area but rare everywhere else. Other diseases, such as many rare forms of cancer, have no apparent pattern of distribution but are simply rare. The classification of other conditions depends in part on the population being studied: All forms of cancer in children are generally considered rare, because so few children develop cancer, but the same cancer in adults may be more common.
Rare diseases are usually genetic and are therefore chronic. EURORDIS estimates that at least 80% of them have identified genetic origins. Other rare diseases are the result of infections and allergies or due to degenerative and proliferative causes. Symptoms of some rare diseases may appear at birth or in childhood, whereas others only appear once adulthood is reached.
CheckOrphan and CheckRare’s Rare Disease Database provides brief overviews to more than 600 rare diseases. This is not a comprehensive database since there are nearly 7,000 diseases considered rare in the U.S. We add new topics as we are able to do so, with the help of rare disease medical experts. Inclusion in our list does not serve as official recognition as a rare disease and should not be used to assume that a disease is rare.
If you are seeking additional information about a rare and neglected diseases that are not in our database, please contact the Genetic and Rare Diseases Information Center (GARD) at the National Institutes of Health.
- Bacterial Infections
- Behavioral And Mental Disorders
- Blood Diseases
- Chromosome Disorders
- Congenital And Genetic Diseases
- Connective Tissue Diseases
- Digestive Diseases
- Ear, Nose, And Throat Diseases
- Endocrine Diseases
- Eye Diseases
- Female Reproductive Diseases
- Fungal Infections
- Heart Diseases
- Hereditary Cancer Syndromes
- Immune System Diseases
- Kidney And Urinary Diseases
- Lung Diseases
- Metabolic Disorders
- Mouth Diseases
- Musculoskeletal Diseases
- Nervous System Diseases
- Newborn Screening
- Nutritional Diseases
- Parasitic Diseases
- Rare Cancers
- Rare Diseases Clinical Research Network
- Skin Diseases
- Unknown Origin
- Viral Infections