Rare Diseases 101

What is a rare disease?

Unlike common diseases, a rare disease affects a relatively small number of individuals. There is no common internationally or even nationally accepted definition of what a rare disease is. In Canada, the European definition is commonly used, which states that a disease is considered rare if it affects fewer than 1 in 2,000 individuals. While estimating the exact number of rare diseases is challenging due to various factors, including the evolving nature of medical research and the discovery of new conditions, it is prominently cited that there are more than 7,000 – 10,000 different rare diseases.

The increasing precision of genomic technologies means that new diseases are being discovered regularly. While individual diseases may be uncommon individually, the total number of people in Canada affected by a rare disease is not. Collectively, they are estimated to affect 1 in 12 people in Canada which equates to over 3 million, with two-thirds being children.

Approximately 80% of rare diseases are genetic, often present from birth. More than one-third of these diseases remain unsolved, meaning that their genetic cause is unknown. Some rare diseases are well-documented and thoroughly studied, while others are extremely rare, with only a handful of cases reported worldwide.

Rare diseases, like many other chronic diseases, are serious, debilitating, and progressive, requiring life-long management. They typically display a high level of symptom complexity and thus are a significant cause of ongoing health and psycho-social challenges. There is no cure for many rare diseases, so improving quality of life and extending life expectancy of people living with a rare disease relies on appropriate treatment and care.

What are some of the challenges faced by those affected by a rare disease?

Delayed Diagnosis

Many rare diseases are difficult to diagnose, leading to delays in receiving appropriate medical care. Misdiagnoses and a lack of awareness among healthcare professionals contribute to the diagnostic odyssey experienced by patients.

Limited Treatment Options

The rarity of these diseases often means that there are limited treatment options available. Research and development of therapies for rare diseases may be neglected due to the small patient populations.

Isolation and Lack of Support

Patients with rare diseases often feel isolated because these conditions are not well-known. Support networks may be limited, and patients may struggle to find others who understand their experiences.

Psychosocial and Financial Impact

Dealing with a rare disease can take a toll on mental health and wellbeing of both patients and their families. Coping with uncertainty, managing chronic symptoms, and navigating the healthcare system can contribute to stress and anxiety. Rare diseases also pose a significant financial burden due to specialized medical care, medications, and sometimes travel for expert consultations.

Lack of Research and Clinical Trials

Limited research on rare diseases means that there may be a lack of understanding of the underlying mechanisms and optimal treatment strategies. Additionally, the small patient populations make it challenging to conduct clinical trials.

Healthcare System Navigation

Navigating the healthcare system can be challenging for individuals with rare diseases. Coordinating care among various specialists and accessing appropriate resources may require considerable effort. Canada’s federated healthcare system, where health delivery and coverage are managed provincially and territorially, adds further complexity and inequities.

Why is the zebra the global symbol?

In medical school, students are often taught: “When you hear hoofbeats, think horses, not zebras” (coined in the 1940s by Dr. Theodore Woodward, professor at the University of Maryland School of Medicine) — a reminder to look for common conditions first. But in the world of rare diseases, sometimes it is a zebra.

Just like no two zebras have the same stripes, every rare disease and every patient is unique. The zebra symbolizes the need to look beyond the usual, to recognize the rare, and to ensure timely diagnosis, care, and support for those often overlooked.

Looking for more information about rare diseases?

There are different resources available that provide information on specific rare diseases. Among them, the following are good places to start:

The Canadian iRARE Centres offers free, bilingual, and confidential support provided by a professional.
The Genetic and Rare Diseases Information Center (GARD) provides comprehensive information about rare and genetic diseases.
Orphanet is a portal for rare diseases and orphan drugs.