You might not know it, but your pinky might contain a feature that's extremely rare and little understood. It’s called an extra interphalangeal transverse, and it simply consists of a third crease on the little finger.
Also known as a supernumerary digital flexion crease, it’s typically found below the crease that’s created by the main bend in the little finger, just above where a ring would sit. While the small amount of research into extra finger creases has looked at them occurring on the little finger, additional grooves have been documented on other fingers too.
If your finger has this harmless little glitch, you should consider it a true rarity.
In a study of the phenomenon from Japan in 1978, scientists gathered 551 people and counted their pinky creases. Of the 1,102 little fingers studied, just six were found to have an extra transverse crease. Interestingly, the extra creases were only found on a single little finger in the male participants with the feature, but they were seen on both little fingers among the females.
Another study suggested that it might be slightly more common in males than females, but that was based on a single group of 307 people in India.
Skin creases are related to the way connective tissue is attached to the underlying bone. There typically seen at the joints, as this is where connective tissue has to be anchored to underlying structures. However, people with an extra interphalangeal transverse don’t have an additional joint in their fingers.
There’s little idea of why some people are endowed with extra creases in their fingers. Some studies have attempted to link it to certain health complications, but a clear and direct relationship with any single condition has never been found.
In other words, there's no need to freak out if you've only just discovered you're armed with an extra pinky crease.
Genetics potentially has some influence on it, although there’s no record of scientists ever looking into this. After all, this is not exactly a burning question of biomedical science.
The study of extra interphalangeal transverse might have some practical implications, however.
A 2015 study highlighted how the feature could be used in the field of forensics. For instance, if the handprint of an assailant features an extra crease, then it should theoretically be easy to narrow down the list of suspects. Likewise, the additional crease could be used as a feature that helps to identify a victim or missing person, just like a distinctive scar, mole, or tattoo.
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The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.