Rare diseases: what they are, which and how many and how science has helped patients to deal with them.

The European Union classifies as rare a disease that affects less than one person in 2,000. In the United States a disease is rare if it affects less than 200,000 of the total population of the country. In Japan, the criteria are different: every disease that affects one person in 2,500 is considered rare.¹

Facts and figures.

There are more than 7,000 types of rare and genetic diseases catalogued, which affect more than 400 million people worldwide² of which more than 13 million are in Brazil. However, as most rare diseases are unscreened, it is difficult to determine the exact number of rare diseases or how many people are affected for sure.³ Researching and developing treatments for these diseases is a unique challenge: in the US 95% of rare diseases does not have an FDA-approved product for treatment.

The causes of rare diseases

Most rare diseases are believed to have genetic causes: gene variations and mutations. In some cases, genetic mutations are transmitted from generation to generation, in others they are produced randomly and a person may be the first of a family diagnosed with a certain disease.³

the most common rare

The diseases with the highest number of approved therapies in the US include dwarfism, Lennox-Gastaut syndrome (a particular type of epilepsy) and cystic fibrosis.

In Brazil, the most common rare disease is the fragile-x syndrome – an X-linked intellectual disability that also causes behavioral changes such as hyperactivity and attention deficit.

But there are others, like the hereditary angioedema – disease is caused by a change in the gene that produces a protein called C1-esterase inhibitor, which causes swelling in the extremities of the body, face, genitals, intestinal mucosa and larynx; The spinal muscular atrophy – a progressive, genetic disease that causes problems with motor neurons and leads to progressive muscle weakness; The osteogenesis imperfecta, also called glass bones – the body's inability to produce or synthesize collagen type 1, which has the function of giving strength and support to the bones; and the mucopolysaccharidoses – a group of 11 inherited metabolic diseases caused by a failure in the production of enzymes responsible for the digestion of complex sugars, the lack of which affects many of the body's systems and causes organ damage.⁴

How science has helped.

Since the US enacted the Orphan Drug Act in 1983, the diagnosis, treatment and prevention of a variety of rare diseases has come a long way.

Many biotechnology and pharmaceutical companies have been developing drugs for rare diseases in recent years. New data and approaches such as gene therapy have also made monogenic diseases easier to track. In addition, regulatory and legislative initiatives in each country have encouraged research and development, and there are currently many more products under development.

In a July 2020 Pharmaprojects® report, there are 27 rare congenital and genetic diseases with at least ten products in active development. Another 153 conditions have at least one product in active development.

Between 1973 and 1983, fewer than 10 treatments for rare diseases were approved. Since 1983, more than 400 medicines and biological products for the treatment of rare diseases have been placed on the market.³

In this scenario, with so many and so varied rare diseases and drugs available, it is important not only to identify the appropriate treatment for each type of disease, but also to facilitate access to the patient, since in many cases the drugs are not produced or sold in the country.

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References:

1. Global Masters. Rare Congenital and Genetic Diseases; they deserve a better future. Available in:
   https://www.mastersglobal.com/news-events/rare-congenital-and-genetic-diseases-they-deserve-a-better-future/ Accessed in November 2021.
   2. Global Genes. Rare Facts. Available in: www.globalgenes.org/rare-facts/ Accessed in November 2021.
2. NIH – National Center for Advancing Translational Sciences. Most Frequently Asked Questions About Rare Illnesses. Available in: https://rarediseases.info.nih.gov/espanol/pages/157/preguntas-mas-frecuentes-sobre-enfermedades-raras Accessed in November 2021.

4. R7 Health. Find out which are the most common rare diseases in Brazil. Available in: https://noticias.r7.com/saude/fotos/saiba-quais-sao-as-doencas-raras-mais-comuns-no-brasil-27022018#/foto/1 Accessed in November 2021.