A rare disease or an orphan disease is a medical disorder that occurs in a very small fraction of the population, usually with a broad variety of signs and symptoms, scarce medical experience, and with few easily available treatments because they are infrequently encountered; most rare disorders have a genetic etiology and are chronic, progressive, and occasionally life-threatening, which creates a large problem for diagnosis and treatment management for families and patients.
Genetic origin: The majority of rare diseases arise from genetic mutations and are thus typically present throughout an individual's lifetime.
Diagnostic difficulties: Because they are so rare, they can be problematic to diagnose as their symptoms tend to be subtle or resemble more common conditions, and patients may experience a "diagnostic odyssey" of undergoing several tests before a diagnosis is reached.
Treatment restrains: Sparse studies and small numbers of patients generally result in the lack of, or few effective treatments for rare diseases.
Influence on quality of life: The chronic course of most rare diseases can significantly influence an individual's quality of life, with effects on his/her daily routine, work, and social interaction.
Examples of rare diseases: Cystic Fibrosis, Huntington's disease, Muscular dystrophy, Osteogenesis imperfecta, Rett syndrome, and Neurofibromatosis.
Key features of the management of rare diseases:
Patient advocacy groups: Organizations dedicated to particular rare diseases may be important in generating awareness, funding research, and offering information to families and patients.
Genetic testing: Technological advances in genetic testing can greatly enhance diagnosis in rare diseases.
Orphan drug development: Drug manufacturers are encouraged to create treatments for rare diseases by "orphan drug" designation, which offers regulatory and economic support.
Caused due to mutations & abnormalities in DNA.
Can occur due to spontaneous Mutations or can be inherited from parents to their children.
TYPES OF GENETIC RARE DISEASES:
Single Gene Disorders:
Also called 'Monogenic Diseases'.
It is caused due to mutation in single gene only.
Examples:
(i) Cystic Fibrosis – Affects the lungs and digestive system.
(ii) Huntington’s Disease – Affects the brain, causing movement and cognitive issues.
(iii) Sickle Cell Disease – Causes misshaped red blood cells leading to pain and organ damage.
Mitochondrial Disorders:
Mutation in the DNA of mitochondria can cause this type of rare genetic diseases.
Examples:
(i) Leigh Syndrome – Affects the nervous system and causes developmental delays.
(ii) MELAS Syndrome – Causes muscle weakness, stroke-like episodes, and seizures.
Chromosomal Disorders:
Due to addition or deletion or abnormal chromosome.
Examples:
(i) Down Syndrome – Caused by an extra copy of chromosome 21.
(ii) Turner Syndrome – Affects females due to a missing or incomplete X chromosome.
(iii) Cri du Chat Syndrome – A rare disorder caused by the deletion of part of chromosome 5.
Complex Genetic Disorders:
Multiple genetic and environmental factors contributes in causing this type rare disease.
Examples:
(i) Ehlers-Danlos Syndrome (EDS) – Affects connective tissues, leading to hypermobility and fragile skin.
(ii) Marfan Syndrome – Affects connective tissues, leading to heart and eye problems.
Rare diseases which are not inherited from the parents to their offspring is termed as Non-genetic rare diseases.
Causes are due to environmental, autoimmune, infectious or maybe unknown factors.
1. Infectious Rare Diseases
Caused by - bacteria, viruses, or parasites.
Examples:
(i) Ebola Virus Disease – A deadly viral infection.
(ii) Creutzfeldt-Jakob Disease (CJD) – A rare brain disease caused by prions.
(iii) Nocardiosis – A bacterial infection affecting the lungs, brain, and skin.
2. Autoimmune Rare Diseases
When our healthy immune system starts to mistakenly attack our own body's cells.
Examples:
(i) Myasthenia Gravis – Causes muscle weakness.
(ii) Goodpasture Syndrome – Attacks the lungs and kidneys.
(iii) Paraneoplastic Pemphigus – A severe blistering skin disorder linked to cancer.
3. Environmental & Toxic Exposure Diseases
Caused by environmental factors or exposure to chemicals.
Examples:
(i) Black Lung Disease – Caused by inhaling coal dust.
(ii) Minamata Disease – Caused by mercury poisoning.
(iii) Gulf War Syndrome – A condition affecting veterans due to toxic exposures.
4. Rare Cancers
Cancers affecting a small population.
Examples:
(i) Ewing Sarcoma – A rare bone cancer.
(ii) Merkel Cell Carcinoma – A rare and aggressive skin cancer.
(iii) Chordoma – A tumor in the spine or skull.