It’s been almost a year since my diagnosis, and I’ve been wondering – since almost day 1 – whether there’s some reason why I ended up with Complex Regional Pain Syndrome (CRPS). Or Reflex Sympathetic Dystrophy (RSD), the old name for it that some doctors seem to prefer. Could there be a genetic factor, some predisposition to this rare and nasty disease?
I have red hair and blue eyes, which the rarest combination of colouring. One of my red-headed relatives told me that we’re only about 0.17% of people worldwide.
That’s about 13,000,000 out of about 7,600,000,000 people on our planet! Put another way, only 13 million – of our global population of 7.6 billion people – have both blue eyes and red hair.
The red hair alone is rare, at (I think) about 1% to 2% of the global population. It’s more common in Ireland and Scotland; I think the percentage of redheads in those areas goes up as high as 40%. And that’s where part of my family came from, to Canada, a long time ago; from the Scottish Highlands.
So I can’t help but wonder whether that rare combination is somehow tied to the fact that I’ve ended up with a disease that’s… rare. I know this may simply be a coincidence, but it’s still an intriguing idea. The red hair is due to a genetic mutation of the melanocortin 1 receptor; called MC1R for short.
Because my background’s in clinical (medical) research ethics, my first thought is always: “Has any research already been done on this?” So I checked websites listing research projects, and all I could find were a couple of old-ish articles.
The oldest one is from 2003, in a scientific journal called the Proceedings of the National Academy of Sciences. That makes it almost 15 years old, which is kind of ancient in the world of medicine! Nevertheless, that study was intriguing because it said that:
At present, a number of biological roles of MC1Rs are widely recognized: regulation of pigmentation and hair color in mammalian melanocytes; regulation of sun sensitivity, freckling, and skin cancer risk; and antiinflammatory effects…
MC1Rs are expressed in brain glial cells and neurons of the ventral periaqueductal gray, a brain area of critical relevance to the modulation of nociception. Thus, although the involvement of MC1Rs in analgesia is surprising, it is not inexplicable.”(1)
Nociception isn’t a very common word. It’s how the nervous system warns our brains about possible threats. If you’ve ever felt pain because your foot was too close to a campfire, that would have been nociception at work; telling you to move your foot!
It’s how your nervous system sends a warning – a pain signal – to your brain. This is really important to keep us safe, but in chronic pain diseases that nociception goes somewhat out of control; it goes haywire.
And when this article mentions ‘and antiinflammatory effects’, what they mean is that this gene mutation can affect how a person’s body reacts to inflammation. CRPS is a neuro-inflammatory disease, so maybe there’s some kind of a genetic link there.
But this study didn’t specifically mention CRPS, nor did it come up with any definitive proof that MC1R is linked to neuropathic (nerve) pain. And that’s the worst kind of pain that I have from this disease, among about seven different types of pain I feel on any given day. It really is a nasty disease!
The other study that I found is from 2004. So again fairly old, at least in terms of medical research. This one was titled: Anesthetic Requirement is Increased in Redheads.(2) Sounds intriguing, right? This medical journal article said that:
Anesthetic requirement in red heads was increased 19%, a difference that was highly statistically significant (P = 0.0004).
The results confirm anecdotal clinical impressions that anesthetic requirement is greater in redheads.”(2)
In plain English, there were rumours that redheads were more sensitive to pain than blondes and brunettes. This study found that redheads needed almost twenty percent (or one fifth) more anesthesia for surgery than patients without red hair.
This article ends with this statement:
In summary, our results confirm anecdotal clinical impressions that anesthetic requirement is greater in redheads.
The observed 19% difference between the two groups makes red hair a distinct phenotype that correlates with inhalational anesthetic requirement in humans and can be traced to a specific genotype.”(2)
So it seems that there might be a genetic predisposition to pain sensitivity. This fits in with my idea that CRPS could be related to the MC1R genetic mutation. I’ll be keeping an eye out for more research on this topic, as it could lead potentially lead to genetic screening tests or better treatments.
As always, thanks so much for reading. Feel free to drop me a line over on Instagram or Twitter; I’ve sadly had to disable the comments feature here, after being bombarded with obscene images from what appear to be Chinese and Russian trolls.
Have a happy day, and take a moment enjoy the sights, smells, and sounds of springtime 😉
References
(1) Mogil, Jeffrey S, et al. The melanocortin-1 receptor gene mediates female-specific mechanisms of analgesia in mice and humans. Proceedings of the National Academy of Sciences of the United States of America. Vol. 100,8 (2003): 4867-72. Accessed 22 Apr 2017. Web:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC153647/
(2) Liem, Edwin B et al. Anesthetic requirement is increased in redheads. Anesthesiology. Vol. 101,2 (2004): 279-83. Accessed 22 Apr 2017. Web:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1362956/