Rare Diseases and Comorbidities: Which One Is Causing My Symptoms?!

Living with a rare disease can come with a variety of comorbidities. It is difficult to know what to expect in terms of comorbidities for a person with a rare disease. It is more difficult to conduct research on rare diseases since there are fewer patients suffering from them than from other diseases that have higher numbers of diagnosed patients.

When living with the symptoms of a rare disease, in addition to a comorbidity, it is hard to know what disease is causing which symptoms. For example, I suffer from type 1 narcolepsy, also known as narcolepsy with cataplexy.

Is this symptom from my rare disease or a comorbidity?

In my case, as a person with narcolepsy, I am more likely to suffer from attention-deficit/hyperactivity disorder (ADHD) symptoms and major depressive disorder.^1,2

As a person with narcolepsy, I can experience symptoms of brain fog or an inability to focus on a task. This can be interpreted as ADHD symptoms OR narcolepsy symptoms! Additionally, as a person with narcolepsy, I can struggle to get out of bed in the morning, sometimes spending days at a time sleeping more often than I am awake. This can look like narcolepsy symptoms OR major depression symptoms!

What does this mean?

The impact on rare disease diagnosis

People with narcolepsy might go undiagnosed for long periods of time due to their symptoms looking like more common conditions, like ADHD or major depressive disorder. Doctors may pin these conditions down as the source of the symptoms when in reality, there is much more going on than meets the eye.

This can significantly slow down the amount of time that it takes to be diagnosed with a rare disease. For example, it takes an average of 8 to 10 years to be diagnosed with narcolepsy.³

Why do medical screenings sometimes miss rare diseases?

As mentioned before, it is difficult to know whether or not comorbidities are the source of symptoms rather than the rare disease itself. This has far-reaching effects, including, in the case of narcolepsy, an increase in the time that it takes to get a rare disease diagnosis.

Fewer people suffer from rare diseases than more common ailments, which means fewer people are available for researching rare conditions. Specific research efforts are needed to prove any links with common comorbidities. So, when the research is nonexistent or very sparse, comorbidities are difficult to prove. It feels like most of the time we are simply guessing what condition is causing which symptoms. For me, someone who suffers from narcolepsy, this can look like:

• "Am I unable to focus today because of my hyperactivity? Or am I unable to focus today because I’m so tired I can barely hold my eyes open?"
• "Am I wanting to stay in bed because I’m depressed? Or am I wanting to stay in bed because I am in desperate need of restorative sleep?"

More unanswered questions

Another example of a possible comorbidity with narcolepsy is dementia. A link has not been proven, yet studies show that other sleep disorders, like insomnia, can increase a person’s chances of developing dementia.^4,5

People with narcolepsy, including me, often experience insomnia at night in addition to being sleepy during the day. Does this mean that we are at higher risk of developing dementia? We can't be sure, because the research just isn't there yet. I hesitate to bring this subject up in my narcolepsy community because I don’t want to spread misinformation or cause people to stress over things they cannot control. Yet, this is a subject that I often think about when it comes to living with narcolepsy.

It is hard not knowing the source of the symptom

It can be easy to focus on what we don’t fully understand or know about our rare disease. However, when I am feeling overwhelmed by symptoms and possible comorbidities, I find it helpful to focus on the things within my control.

I may not be able to focus, or sleep, or get out of bed – but the source of the symptoms doesn’t matter. What matters is how I choose to respond to the symptoms. If I accept my symptoms as they are, regardless of where they are coming from, I can find a degree of comfort in this acceptance.