Fingerprints are so familiar that they are mostly taken for granted. Except, however, for people who don't have any at all. Although rare, such a deficiency poses a problem for immigration, the border patrol and the criminal justice system, which all rely on tools such as biometric scans and other devices that read these tiny, unique, markings found on the hands and fingertips of most people.
A recent study in The American Journal of Human Genetics claims to have found a gene associated with the absence of fingerprints. People with this condition, called adermatoglyphia, suffer from no other health effects except, perhaps, frequent headaches at border control.
"It's barely a disease—the people who have it are perfectly healthy," says Eli Sprecher, lead author of the study and dermatologist at the Tel Aviv Sourasky Medical Center in Israel. "The only difficulty they experience is trying to cross the border." In fact, it was just such a hassle experienced by a 29-year-old Swiss woman at the U.S. border (waiting for hours as puzzled officers tried to make sense of her missing prints) that first brought this condition to Sprecher's attention. It has, appropriately, been dubbed "immigration-delay disease."
But if this condition causes hassles at security, people with adermatoglyphia don't show their stress very easily—their hands sweat less than normal. Terry Reed, a human geneticist (emeritus) at the Indiana University School of Medicine, thinks this may be related to how the mutation affects the development of fingerprints.
Typically, the pores of sweat glands lie along the tiny ridges that make up our fingerprints. For people with this mutation, "the ridges don't even form to begin with, so that's going to interfere with sweat glands," Reed says.
To find the mutation, Sprecher and colleagues at the University Hospital Basel in Switzerland, looked at 16 members of a Swiss family—nine with the condition, seven without. A genetic analysis revealed the culprit to be a mutation in the gene SMARCAD1, specifically in a small portion that codes for a protein only synthesized in the skin.
Immigration-delay disease is very rare—it has only been documented in four families across the world. But there are several other more complex syndromes that can also result in missing fingerprints. One is Naegeli syndrome, an inherited disorder that affects the skin, sweat glands, nails and teeth. Another is dyskeratosis congenita, a rare bone marrow disorder accompanied by much more serious effects such as early aging and predisposition to cancer.
Whether they are genetically caused or not, missing fingerprints are a serious concern for forensic scientists. "We often deal with people whose fingers have been damaged in some way, or who are attempting to hide their fingerprints," says Glenn Langenburg, a certified latent print examiner at the Minnesota Bureau of Criminal Apprehension. "It can be quite a problem."
Attempting to eliminate or disfigure your unique identifiers has a long history among criminals, some of whom have gone to some extreme lengths to avoid identification. In the 1930s, kidnapper Theodore "Handsome Jack" Klutas took a knife to his fingerprints in the first documented case of finger mutilation, and the notorious bank robber John Dillinger dipped his fingers in acid to burn his prints off.
But according to Langenburg, there are many cases of people unintentionally losing their fingerprints. Agricultural workers, whose hands are often heavily callused or full of sores, as well as masonry workers or bricklayers, who handle heavy rough materials all day long, are two groups that often have the most difficulty in providing a clear fingerprint.
"Literally they're just black smudges," Langenburg says. Even wholly absent fingerprints, however, don't eliminate all identifying marks whatsoever. First of all, the same ridges you have on your fingertips continue down your finger and onto your palm, and are also present on the soles of your feet.
"We can identify you just as easily by your palm as we can by your finger," Langenburg says. Also, ridges are not everything—each crease and fold in your hands and feet forms a unique pattern, which forensic scientists can use for identification. Whether it's a gene mutation, corrosives or hard labor that eliminates ridges, crease and other patterns are just as usable, according to Langenburg. That pattern also stays with you for your entire life, so even newborn babies (whose ridges are so fine they are often almost impossible to capture with ink or an electronic scan) can still be identified by the hairline creases on their hands and feet.
Scientists hope that studying curious conditions such as immigration-delay disease may help us understand how fingerprints develop normally, particularly the genes and proteins involved in that process. There is still much to be understood about the formation of fingerprints, or even why we have them in the first place.
Originally thought to increase friction and allow for a firmer grasp, recent research suggests that the fingertip ridges may increase sensitivity to fine sensations.
"[Fingerprints] may be a way to augment the contact surface between our body and the external environment," Sprecher says. So rather than improving grip, they may improve one's tactile sense.
But the jury is still out. "To be honest, we don't really know what the function of fingerprints is," Reed says. "We do know that humans are the only ones that have really complex patterning…and that they're fascinating."