There are "better known" rare diseases such as cystic fibrosis, hemophilia, and lysosomal diseases that are included in Chile's Explicit Health Guarantees (GES) Law or in the "Ricarte Soto" Law which covers some high-cost medications and devices. But there are other "ultra rare" diseases, which are less well known and are not covered by the health system. Many of these ultra-rare diseases cause birth defects or intellectual disability, are serious, and can lead to early death. Because there is little information about them, they can be harder to identify, confirm, treat, and educate about.

The therapeutic trajectory is the sequence of care events that a person follows from the moment they enter the health care system. For example, the professionals one sees, the laboratory or imaging tests one has, the places where one seeks help, etc. It helps to visualize the unique experiences for each individual within the health system and the provision of care, as well as health experiences that occur outside the health system, such as contact with groups who share the same issues, and the relevance and value perceived by people with rare diseases and their families.

Given that rare diseases are complex and infrequent, the search trajectory for a clear diagnosis and therapeutic guidelines is often long, difficult, costly and emotionally exhausting. Therefore, people with rare diseases and their families report experiencing a “diagnostic odyssey,” which is a complex sequence of health care touchpoints, from the point of entry into the health system until obtaining (or not) a clear diagnosis.

Tacit or implicit knowledge is what people and families of those living with a rare disease develop as insight and experience throughout their lives in order to adapt, understand, integrate and accept their health condition in their day-to-day life. Tacit or implicit knowledge refers, then, to people who are experts by experience.

Health-related quality of life is "the influence of health status, health care, and health promotion on an individual's ability to maintain a level of functioning that allows them to perform activities that are important and affect general well-being " (Shumaker and Naughton 1995). It includes the dimensions of social, physical, and cognitive functioning, mobility and self-care, and emotional well-being. This indicator helps to learn the state of health of people and the impact that diseases have on them.

This standardized questionnaire measures self-perceived health status and/or health-related quality of life. It was developed by the EuroQol (EuroQol Research Foundation, 2019) and translated into multiple languages, including Spanish. It consists of five questions and a visual scale for people to indicate how they perceive their health. If you want to know more about this instrument, we invite you to watch this video.

There are an estimated 7,000 known rare conditions. Although each one affects a few individuals, when we total them, rare diseases can affect up to 5% of the population or 1 million people in Chile. If we consider that the entire world has approximately 7 billion people, about 350 million people may have a rare disease. This would be the equivalent to the third most populous country in the world.

There are many types of rare and infrequent diseases. Most (80%) are genetic, that is, the person has a change in one or a few genes, which are the instructions for forming all body parts or their functions. Some people have rare cancers, infections by rare agents (such as Hantavirus), or immune system disorders.