Rare Disease
04.20.2026
Living with a rare disease can be a difficult ordeal, both physically and mentally1 — a reality that William Fung tries to prepare his patients for in his practice.
As a rheumatologist at Toronto’s North York General Hospital,2 Dr. Fung regularly sees adults with a variety of rheumatologic conditions — including Immunoglobulin G4-related disease (IgG4-RD), a rare autoimmune disease3 (as Dr. Fung explains in the video here, a rare disease is one that affects fewer than one person in 2,0004).
“IgG4-related disease is a rare autoimmune disease that causes a combination of inflammation and scarring,” Dr. Fung explains.2 The symptoms and the organs affected can be different from person to person.3 “[It] can affect a lot of different organs, such as the salivary glands or the pancreas. It's a little bit different in everyone. So how it comes out is unique for every single case.”5,6
For doctors, helping people with a rare disease can be a challenge because they simply don’t know much about the condition and haven’t spent a lot of time treating it. “Treating rare diseases is difficult. I think it's a moment of vulnerability for us. We're used to knowing what to do most of the time in a particular situation when we see a patient, but when it comes to rare diseases, we don't really have the same level of experience or the amount of research that we're used to relying on,”7 Dr. Fung acknowledges.
So how does Dr. Fung give patients hope? For one thing, he tells them about the rising tide of interest in rare diseases among the medical community, and from patient support groups.8 “It’s such an exciting time, to see all the recent interest in rare disease,” he says. “We're seeing a lot of increasing interest in rare diseases and there's a lot of innovations that are coming out.c And I think truly what we're seeing is that advances in the medical sciences are giving us new approaches to the way that we treat these patients.”
Listen as Dr. Fung explains the importance of telling people with rare diseases that they’re not alone — that their voices are heard.
Interview with Dr. William Fung
My name is Dr. William Fung.
I am certified with the Royal College of Physicians and Surgeons in internal medicine, and I did a fellowship in rheumatology at the University of Toronto.
As part of my practice, I see adult patients with rheumatological disease.
So this includes things like rheumatoid arthritis or lupus.
But on top of that, I also see patients with rare disease like IgG4-related disease.
IgG4-related disease is a rare autoimmune disease that causes a combination of inflammation and scarring.
And it can affect a lot of different organ systems, like the salivary glands or the pancreas.
And the way it presents in every single person is different.
Rare diseases affect fewer than 1 in 2,000 people.
And although that number can seem small, what that translates to is about 300 million people worldwide.
For health care providers, what that means is that it can be difficult to diagnose and also to treat these patients.
I think as a clinician, treating patients with rare diseases is difficult because it's a rare moment of vulnerability.
I think we're used to at least most of the time, knowing the answers and knowing what to do.
In the case of rare disease, we don't always have those answers, and we don't have a lot of experience or research to lean back on.
And so it ends up being a moment where we have to be very transparent with our patients and really going along that journey together.
When I interact with patients with rare disease, the approach I like to take is to make sure that I'm as transparent with them as possible.
I think it's a journey that can be very difficult, and it takes a lot of perseverance and grit.
And at the end of the day, it's one where we have to build it together and it has to be built on partnership and trust.
And so when I have challenges, I like to be honest with my patients and let them know that there are hurdles in terms of their diagnosis or their treatment.
And I think it should be a relationship where the patients, too, can feel comfortable telling me the troubles that they are running into.
I think the hardest part about the experience for patients with rare disease is just how isolating and lonely it can be.
And for these patients, when they try to get medical attention, it's not always a disease that everyone knows about or a disease that's top of mind.
And so it becomes extremely difficult for them to get the help that they need to get.
The problem that patients with rare diseases face along the way can be multiple.
I think the first inherent difficulty is with diagnosis and the journey to get a diagnosis can be extremely long and challenging.
Treatment, too, can be difficult because treatments for these rare diseases are not always available.
For a patient who has rare disease who is finding the journey difficult, what I would say to them is that you have to persevere.
The journey can be extremely challenging and it can demand a lot of patience.
But the key is you have to continue to engage with the medical community in order to move forward in terms of your care.
I think this point in time for patients with rare diseases is actually very exciting and invigorating.
We're seeing a lot of increasing interest in the rare diseases, and there is a lot of innovations that are coming out.
And I think truly what we're seeing is that advances in the medical sciences are giving us new approaches to the way that we treat these patients.
I think in our jobs as physicians, we have a lot of lows and a lot of highs.
But to have a breakthrough with a patient with a rare disease, I think is one of the highest of highs.
When we see these patients, what we see is that the disease has become the centre of gravity for their lives.
The way they work, the way they plan their lives centres around their symptoms and what's happening with their disease.
And so when we get a breakthrough, what we're able to see is they're able to reclaim those parts of their lives that they lost, like playing with their grandkids or going travelling.
And this is really what makes this job amazing.