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A rare disease is any
disease A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medica ...
that affects a small percentage of the population. In some parts of the world, an orphan disease is a rare disease whose rarity means there is a lack of a market large enough to gain support and resources for discovering treatments for it, except by the government granting economically advantageous conditions to creating and selling such treatments.
Orphan drugs An orphan drug is a medication, pharmaceutical agent developed to treat medical conditions which, because they are so rare, would not be profitable to produce without government assistance. The conditions are referred to as orphan diseases. The as ...
are ones so created or sold. 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 birthdays. With only four diagnosed patients in 27 years, ribose-5-phosphate isomerase deficiency is considered the rarest known genetic disease. No single cut-off number has been agreed upon for which a disease is considered rare. A disease may be considered rare in one part of the world, or in a particular group of people, but be common in another. The US organisation Global Genes has estimated that more than 300 million people worldwide are living with one of the approximately 7,000 diseases they define as "rare" in the United States.


Definition

There is no single, widely accepted definition for rare diseases. Some definitions rely solely on the number of people living with a disease, and other definitions include other factors, such as the existence of adequate treatments or the severity of the disease. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
, the
Rare Diseases Act of 2002 The Rare Disease Act of 2002 is a law passed in the United States that establishes the statutory authorization for the Office of Rare Diseases as a federal entity able to recommend a national research agenda, coordinate research, and provide educ ...
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 the same as that of the
Orphan Drug Act of 1983 The Orphan Drug Act of 1983 is a law passed in the United States to facilitate development of orphan drugs—drugs for rare diseases such as Huntington's disease, myoclonus, ALS, Tourette syndrome and muscular dystrophy which affect small numbers ...
, a federal law that was written to encourage research into rare diseases and possible cures. In Japan, the legal definition of a rare disease is one that affects fewer than 50,000 patients in Japan, or about 1 in 2,500 people. However, the
European Commission The European Commission (EC) is the Executive (government), executive of the European Union (EU). It operates as a cabinet government, with 27 European Commissioner, members of the Commission (informally known as "Commissioners") headed by a P ...
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. The definitions used in the
medical literature Medical literature is the scientific literature of medicine: articles in journals and texts in books devoted to the field of medicine. Many references to the medical literature include the health care literature generally, including that of denti ...
and by national health plans are similarly divided, with definitions ranging from 1/1,000 to 1/200,000.


Relationship to orphan diseases

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 The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...
, "orphan diseases" have a distinct legal meaning. The United States'
Orphan Drug Act The Orphan Drug Act of 1983 is a law passed in the United States to facilitate development of orphan drugs—drugs for rare diseases such as Huntington's disease, myoclonus, ALS, Tourette syndrome and muscular dystrophy which affect small numbers ...
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 erecovered from sales in the United States of such drug" as ''orphan diseases''. The European Organization for Rare Diseases (EURORDIS) also includes both rare diseases and neglected diseases into a larger category of "orphan diseases".


Prevalence

Prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
(number of people living with a disease at a given moment), rather than incidence (number of new diagnoses in a given year), is used to describe the impact of rare diseases. The Global Genes Project estimates some 300 million people worldwide are affected by a rare disease. The European Organization for Rare Diseases (EURORDIS) estimates that between 3.5 and 5.9% of the world's population is affected by one of approx. 6,000 distinct rare diseases identified to-date. European Union has suggested that between 6 and 8% of the European population could be affected by a rare disease sometime in their lives. About 80% of rare diseases have a genetic component and only about 400 have therapies, 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 disease A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
s and
infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
s. An example is
cystic fibrosis Cystic fibrosis (CF) is a rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include Shortness of breath, difficulty breathing and coughing up sputum, mucus as a result of ...
, a genetic disease: it is rare in most parts of
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa Africa is ...
but relatively common in Europe and in populations of European descent. In smaller communities, the
founder effect In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using ...
can result in a disease that is very rare worldwide being prevalent within the smaller community. Many infectious diseases are prevalent in a given geographic area but rare everywhere else. Other diseases, such as many rare forms of
cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Poss ...
, 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. About 40 rare diseases have a far higher prevalence in
Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia Russia (, , ), or the Ru ...
; these are known collectively as Finnish heritage disease. Similarly, there are rare genetic diseases among the
Amish The Amish (; pdc, Amisch; german: link=no, Amische), formally the Old Order Amish, are a group of traditionalist Anabaptism, Anabaptist Christianity, Christian church fellowships with Swiss German and Alsace, Alsatian origins. They are close ...
religious communities in the US and among ethnically Jewish people.


Characteristics

A rare disease is defined as one that affects fewer than 200,000 people across a broad range of possible disorders. Chronic genetic diseases are commonly classified as rare. Among numerous possibilities, rare diseases may result from
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometre The micrometre (Amer ...
l or viral infections,
allergies Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and ...
,
chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
disorders, degenerative and proliferative causes, affecting any body
organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical instruments characterized by sustained tone ** Electronic organ, an electronic keyboard instrument ** Hammond ...
. Rare diseases may be chronic or incurable, although many short-term medical conditions are also rare diseases.


Public research and government policy


United States

The
NIH The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government The federal government of the United States (U.S. federal government or U ...
's
Office of Rare Diseases Research The Office of Rare Diseases Research is a division of the National Center for Advancing Translational Sciences (NCATS) that oversees the Rare Diseases Clinical Research Network and Genetic and Rare Diseases Information Center. History The Offic ...
(ORDR) was established by H.R. 4013/Public Law 107–280 in 2002. H.R. 4014, signed the same day, refers to the "Rare Diseases Orphan Product Development Act". Similar initiatives have been proposed in Europe. The ORDR also runs the Rare Diseases Clinical Research Network (RDCRN). The RDCRN provides support for clinical studies and facilitating collaboration, study enrollment and data sharing.


United Kingdom

In 2013, the United Kingdom government published ''The UK Strategy for Rare Diseases'' which "aims to ensure no one gets left behind just because they have a rare disease", with 51 recommendations for care and treatment across the UK to be implemented by 2020. Health services in the four constituent countries agreed to adopt implementation plans by 2014, but by October 2016, the Health Service in England had not produced a plan and the
all-party parliamentary group An all-party parliamentary group (APPG) is a grouping in the Parliament of the United Kingdom The Parliament of the United Kingdom is the Parliamentary sovereignty in the United Kingdom, supreme Legislature, legislative body of the United Ki ...
on Rare, Genetic and Undiagnosed Conditions produced a report ''Leaving No One Behind: Why England needs an implementation plan for the UK Strategy for Rare Diseases'' in February 2017. In March 2017 it was announced that
NHS England NHS England, officially the NHS Commissioning Board, is an executive non-departmental public body In the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is ...
would develop an implementation plan. In January 2018 NHS England published its ''Implementation Plan for the UK Strategy for Rare Diseases''. In January 2021 the
Department of Health and Social Care The Department of Health and Social Care (DHSC) is a Departments of the Government of the United Kingdom, department of Government of the United Kingdom, His Majesty's Government responsible for government policy on health and adult social care ma ...
published the ''UK Rare Diseases Framework'', a policy paper which included a commitment that the four nations would develop action plans, working with the rare disease community, and that "where possible, each nation will aim to publish the action plans in 2021". NHS England published ''England Rare Diseases Action Plan 2022'' in February 2022.


International

Organisations around the world are exploring ways of involving people affected by rare diseases in helping shape future research, including using online methods to explore the perspectives of multiple stakeholders.


Public awareness

Rare Disease Day is held in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
,
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world ...
, the United States and
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
on the last day of February to raise awareness for rare diseases.


See also

* National Organization for Rare Disorders (NORD) * Undiagnosed Diseases Network (UDN) *
Orphanet Orphanet is a knowledge base dedicated to rare diseases as well as corresponding diagnosis, orphan drugs, clinical trials and expert networks The website is managed by a network of academic establishments from 40 countries, led by Inserm. It con ...
(Online portal for rare diseases and orphan drugs) * ICD coding for rare diseases * List of rare disease organisations * Orphanet Journal of Rare Diseases (academic journal) * Rare Disease Day *
Idiopathic disease An idiopathic disease is any disease with an unknown cause or mechanism of apparent wikt:spontaneous, spontaneous origin. From Ancient Greek, Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approxi ...
* ''
Mystery Diagnosis ''Mystery Diagnosis'' is a television docudrama Docudrama (or documentary drama) is a genre Genre () is any form or type of communication in any mode (written, spoken, digital, artistic, etc.) with socially-agreed-upon conventions develope ...
'' * Health care rationing


References


External links


ICD-11 FAQ

Database of rare diseases
at GARD, The United States Genetic and Rare Diseases Information Center
Database of rare diseases
at
Orphanet Orphanet is a knowledge base dedicated to rare diseases as well as corresponding diagnosis, orphan drugs, clinical trials and expert networks The website is managed by a network of academic establishments from 40 countries, led by Inserm. It con ...

National Organization for Rare Disorders
(United States)
Rare Disease UK

Rare diseases search engine
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