“What’s wrong with your thumb?”
“Can I see them?”
“Did you crush it when you were little or something or is it just a deformity?”
I have heard these questions about my thumb my entire life. Because one of my thumbs is different than the other. Not just different than the other thumbs, but different from most thumbs. Look down at your thumbs right now they probably look something like this:
Okay maybe yours is nicer than mine and you have time to actually take care of your nails, but most thumbs look something like this. But not my right hand thumb. My right hand thumb looks like this:
My right hand thumb is stubby. Growing up, this was just a curiosity. I never really thought much about it. It was just my thumb. Occasionally I would get someone asking if I had an accident when I was small that had crushed it or something. I would assure them they had just grown that way. When bidden I would show my two thumbs beside each other and people would remark how strange it was and that would be that. It wasn’t until recently that I figured out once in for all what was going on with my thumb.
I have a cool genetic variant known as brachydactyly type D (BDD for short). I like the name brachydactyly because it reminds me of something you would name a type of dinosaur. The brachydactyly literally means “shortness of the fingers and toes” and the type D refers to it being in the thumbs. It is more commonly known as “clubbed thumb” or “stub thumb”. Other names for this are “Potters thumb”, “shovel thumb”, “royal thumb”, “toe thumb”, or more ominously – the “murderers thumb”.
This type of thumb is sort of rare with only 0.4% of the population of Caucasian people in America having it. That’s like 4 out of 1000 people. And of those 4 out of 1000 people who have it, 3 of them have it on both thumbs. But not me. I’m the one out of 1000 that has just one stubby thumb. I don’t have any other fingers or toes that are affected by it. In other populations the prevalence can be up to 4% of the population.
After a bit of researching I figured out that brachydactyly type D is caused by a variant in the HOXD13 gene. It actually causes a skeletal change in the terminal phalanx of my thumb that just made it grow this way. I don’t call it a mutation because I don’t think there’s anything wrong with it, its just the way my thumbs grew. It can be autosomal dominant with variable expressivity and penetrance. It tends to have more of a complete penetrance in women so women are more likely to have it than men.
How I figured out that I had brachydactyly was through the mass media. Someone was looking at my thumbs saying how weird they were when someone else remarked, “Oh, they’re like Megan Fox’s thumbs!”. So I looked up Megan Fox’s thumbs. And sure enough, there was her thumb looking stubby just like mine. I was astonished by all the negative things that people had to say about Megan Fox’s thumbs. She was included on one list of celebrity’s with deformities. I find this offensive because I do not consider my thumb to be a deformity. (Though my thumbs do make certain things harder, ex. I cannot light a lighter with my right hand thumb) Others have embraced her thumb. There’s even an entire website dedicated to her thumbs. (It has since been taken down).
And this is for good reason since one of the nicknames for the brachydactyly thumb is “Royal Thumb”. It is rumored that this type of thumb was common in the royal bloodlines of Europe, hence the name. The more ominous sounding “murderers thumb” comes from palm reading where the stubbed thumb is supposed to be a sign of an impulsive and angry and explosive nature, leading to murder. Overall I like the “Royal Thumb” better.
Growing up, my Mother was the worst for pointing out the differences in my thumbs. She would always grab my hands, feeling my stubby thumb with her fingers and frowning. It annoyed me then because I didn’t think it was a big deal. Little did I know that my Mother was certain that she must have crushed it when I was a baby and didn’t realize it. She was looking at thumb, full of guilt for something she couldn’t remember doing. She was the most excited when I told her that it was from brachydactyly and that I really was born that way. I hope this article will bring peace of mind to everyone out there that wonders what is up with their weird thumb(s).