A rare disease also referred to as an orphan disease, is any disease that affects a small percentage of the population.
Most rare diseases are genetic, and are present throughout a person’s entire life, even if symptoms do not immediately appear.r. Many rare diseases appear early in life, and about 30 percent of children with rare diseases will die before reaching their fifth birthday. With a single diagnosed patient only, ribose-5-phosphate isomerase deficiency is considered the rarest genetic disease.
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. In smaller communities, the founder effect 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, 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.
Characteristics of Rare diseases.
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.
Symptoms that vary not only from disease to disease but also from patient to patient suffering from the same disease.Relatively common symptoms can hide underlying rare diseases leading to misdiagnosis and delaying treatment. Quintessentially disabling, the patients quality of life is affected by the lack or loss of autonomy due to the chronic, progressive, degenerative, and frequently life-threatening aspects of the disease. The fact that there are often no existing effective cures adds to the high level of pain and suffering endured by patients and their families.
The lack of scientific knowledge and quality information on the disease often results in a delay in diagnosis. Also the need for appropriate quality health care engenders inequalities and difficulties in access to treatment and care. This often results in heavy social and financial burdens on patients.
As mentioned, due to the broad diversity of disorders and relatively common symptoms which can hide underlying rare diseases, initial misdiagnosis is common. In addition, symptoms differ not only from disease to disease, but also from patient to patient suffering from the same disease.