The Curious Case of the Stubby Thumb

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Photo: A BDD thumb (left) and a normal thumb (right)

by Rosa Lin/Medill News Service

“What happened to your thumb?”

“Did you accidentally smash it in the door?”

A thumb was outstretched in the circle of sixth-graders. It had a most peculiar shape, being relatively thin and normal near the base, and then suddenly capped off with a bulbous, short tip, reminiscent of a slightly flattened pearl onion.

The thumb belonged to 10-year old me.  And I was showing it off proudly among my bemused friends.

“See, the other one's like this too!” I stretched out its equally short and bulbous sister. Everyone gaped, laughed, and held the thumb up for inspection.

“You must've bitten your fingernails too often when you were little!”

“Did you jam your thumb playing basketball?”

Why, no, I was born this way. If you're like me, you probably fielded these questions in your youth and wondered whether anybody else in the world has thumbs like yours.

Wonder no more – these thumbs are known in scientific circles as brachydactyly type D, a type of thumb characterized by a shortened distal phalanx (the bone at the tip of the digit) – and we are about to plumb the history, prevalence, myths and genetic basis behind these thumbs.

Most people have a straight, upright thumb, with a nail bed equal to or longer than the nails on their fingers. Some people have a “hitchhiker's thumb” where the tip can bend back almost 90 degrees. Finally, a few people – from 0.10 to 3 percent of a population – have a shortened thumb, a feature colloquially known as club thumb, stub thumb, toe thumb, potter's thumb, hammer thumb and most unappealingly, murderer’s thumb. Fortunately the thumb has been christened neutrally by scientists as brachydactyly type D, so henceforth we shall stick with the designation BDD.

BDD was first characterized by fortune tellers practicing palmistry. According to Angelfire.com's page on Indian palmistry:

"The Murderer's Thumb Unveiled - The clubbed thumb was traditionally called the 'murderer's thumb' denoting the powerful temper of those who carried it. This thumb has a short first phalange (section) and is broad. The tip of the thumb is fleshy and the thumbnail is short and broad. According to those who know, people with clubbed thumbs [however] are strong willed and can control their emotions."

Such a description is rather more palatable than Palmistrylines.com's take:

"This thumb is in a shape of a club. People possessing this type of thumb are animalistic in nature and thought system. They bear brutality of Elementary type. They can harm or murder out of callousness. They lack premeditation and depth."

Ouch! This leads the meeker among the BDD carriers to wonder: why such a dark reputation among chirologists? For the record, chirologists are fortunetellers.

“When these [traits] started getting studied in the late 19th century … there was a push to link [physiological] traits with personality traits. There's no real scientific connection between BDD and any personality trait though,” said Dr. Nathaniel H. Robin, an active clinical genetics practitioner and professor at University of Alabama at Birmingham, who authored a paper on BDD.

BDD is so named because it is one of many traits of brachydactyly, the term given for shortened fingers and toes due to underdeveloped bones in hands and feet. For example, there is brachydactyly type A, where middle phalanges of one, several, or all of the fingers and/or toes are shortened; brachydactyly type B, where distal phalanges and nails of the fingers and/or toes are small or absent; and so forth up to type E. Usually brachydactyly is an isolated trait, meaning that it is not associated with other medical conditions and is generally harmless.

Contrary to what many people with BDD think, BDD “is a fairly common trait,” Robin said. It stays in the population because “it's a benign variant,” meaning it is neither advantageous nor detrimental to those that express the trait.

According to "Abnormal Skeletal Phenotypes," published in 2005 by Alessandro Castriota-Scanderbeg and Bruno Dallapiccola, two prominent radiologists, BDD occurs in 0.4 percent of whites and 0.1 percent of blacks in the United States, with a higher incidence in Israel (1.6 percent of Jews, 3 percent of Arabs) and Japan. In three-quarters of cases, BDD occurs bilaterally, which means it appears on both thumbs, while in the rest of the cases it only appears on one thumb, with the other thumb normal.

There is also a skew among genders. The pioneering human geneticist Julia Bell found in a 1951 study that 60 percent of those affected with BDD were female, while 40 percent were male. The geneticist Robert Stecher confirmed the preponderance for females in a 1957 study. The reason for this may be due to incomplete penetrance, a genetic term that means that a trait fails to express itself even though a person carries the necessary genes. In the BDD case, there is evidence to suggest that the trait has complete penetrance in females and incomplete penetrance in males. BDD is also an autosomal dominant gene, which means a person only needs to inherit it from one parent in order to express the trait.

In the past 10 years, scientists have been able to gain more insight into the genetic basis of BDD. In a 2003 study published in The American Journal of Human Genetics, researchers reported that two mutations in the gene HOXD13 may contribute to BDD.

So who has this trait? One of its most famous carriers is Megan Fox, an actress starring in the "Transformers" movies. She carries the trait on only one thumb, signaling incomplete penetrance. Due to her profile as a celebrity, discovery of her BDD thumb was highly publicized. Russian author and Nobel laureate Alexander Solzhenitsyn is also purported to have at least one BDD thumb. Other people with the trait include: Malin Akerman (US actress), Tory Mussett (Australian actress), Ashley Lynn Cafagna (US actress), and Kristen van Der Noot (Germany DJ and model).

The most speculated of BDD carriers, however, is past European royalty. Despite valiant efforts, I did not find which royals exactly are implicated, so we shall briefly suspend any curiosity along those lines. The European royalty had higher than normal incidence of inbreeding due to a desire to keep their bloodlines “pure.” This resulted in any abnormality or mutation, such as hemophilia, reappearing in higher rates in descendents, instead of being flushed out by a set of significantly different genes. BDD is claimed by some to be a marker of descent from European royalty. However, as BDD occurs all around the world and is both the result of inheritance and random mutation, this, if true, would only apply to a small subset of those with BDD.

“I have no idea” if BDD is linked to European royalty, Robin said. “It may be true – I have no idea.”

At least I have an idea whether mine is linked to European royalty - I'm 100 percent East Asian!

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I have both thumbs and was

I have both thumbs and was mortified when I was young. Now I have found that most people don't notice. I remember in my early 20s realising someone I had recently met had them. I exclaimed "you have my thumbs". She instantly hid them in her fists like I used to. I remember thinking "you don't have to hide them from me." I was really excited. My mum had both and one stub big too. She used to wrap my thumbs tightly when I was little hoping to stop them getting as fat as hers LOL. All it did was kill the quicks on my nails. I had 5 siblings and I was the only one who got them. And my mum had 19 grandchildren, 16 great grandchildren, and 5 great-great grandchildren and no one else has them. Every time a baby is born I check the thumbs. 2(Only one of my nieces has a stub toe). Not sure what that means for the genetic.

I have both thumbs and was

I have both thumbs and was mortified when I was young. Now I have found that most people don't notice. I remember in my early 20s realising someone I had recently met had them. I exclaimed "you have my thumbs". She instantly hid them in her fists like I used to. I remember thinking "you don't have to hide them from me." I was really excited. My mum had both and one stub big too. She used to wrap my thumbs tightly when I was little hoping to stop them getting as fat as hers LOL. All it did was kill the quicks on my nails. I had 5 siblings and I was the only one who got them. And my mum had 19 grandchildren, 16 great grandchildren, and 5 great-great grandchildren and no one else has them. Every time a baby is born I check the thumbs. 2(Only one of my nieces has a stub toe). Not sure what that means for the genetic.

I have one clubbed thumb, my

I have one clubbed thumb, my pinky fingers are so small they don't even go up to the knuckle of the finger they are next to.  All my toes are clubbed The big toes have a regular size toenail the rest I am even scared to trim because if I do then it looks like I don't have a toe nail they are so small.  My biological father has all clubbed fingers and toes but the nails were fine, my brother has all clubbed fingers, thumbs and toes but does not have the toe nail problem I do, all 4 of my daughters have the clubbed toes, no clubbed fingers or thumbs, no toes nail problems, my sister has nothing she has the perfect feet to wear with sandals makes me sick while I have always been teased.

My mother use to tell me my

My mother use to tell me my thumbs were short because I sacked them as a child.  Then one day I noticed not one, but two of my aunts had these short thumbs like me and they never ducked theirs!

My mother use to tell me my

My mother use to tell me my thumbs were short because I sacked them as a child.  Then one day I noticed not one, but two of my aunts had these short thumbs like me and they never ducked theirs!

I am glad I came across this

I am glad I came across this article.  It is nice to know that my thumbs have a name.  I have them on both my thumbs.  I hated it in school growing up, I was teased a lot about them.  I still get self concious about them.  I am hispanic and I get them from my grandmother on my father's side.

I too have both thumbs BDD

I too have both thumbs BDD and have always been self concious about them and tried to hide them. Always check my children and grandchildren, but none have them as yet. Glad to hear I am not alone.  My main concern is GLOVES! There is always an extra piece of  fabric hanging off on the thumbs.

Ever since I was little I

Ever since I was little I always knew there was something "odd" about my fingers, especially because neither my two sisters nor my dad's were the same. But my mom's were. I asked her about it when I was younger but (probably due to a lack of knowledge about BDD) she told me there was nothing "wrong" with my thumbs, but I always felt self conscious about it and would try and hide it as well as I could, scared of what people might think/say about me. Now, I am almost 18 and I still find myself hiding my thumb under my hand when flattened out on a surface in front of other people (habbit), but, what's different is that I know what to say if they might ask. Why didn't I look this up earlier?

This is a hoot!  It may be

This is a hoot!  It may be silly but in a world where everything seems so out of whack, it's rather nice to have a chuckle about weird ass thumbs.  I only have one and was asked many times if it was smashed in a door or window as a child but now I know why it's the way it is... Interesting.  I always referred to it as my king cobra thumb.  Funny to think though that I've never met anyone else with the same type of thumb.  From now on when asked, I'm going to say I'm royalty.

love that I found this!!  The

love that I found this!!  The pic makes me feel like I'm looking at my own thumb!  back in HS the pediatrician told us that it was a trait associated with short stature and that it skips generations.  I'm not aware of my grandparents having this, but they came from large families with many siblings.  My siblings do not have it, but my niece has one thumb.  I have both thumbs and big toes.  My daughter has one thumb that is just slightly broader than the other.  I give it maybe 30% broad based.

Happy to find others like me.  Appreciate the article!  :)

I have this thumb too and for

I have this thumb too and for quite some time my tricked me into thinking it was because i sucked on my thumbs too much!! I think its a pretty cool party show and tell my friends all find it quite funny and i have two friends who also have the same thumb :))

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