Although their physiological role remains obscure, fingerprints (epidermal ridges) are characteristic of the human skin. They are widely used for identity check because their morphology remains permanent without any modification from their establishment at 24 weeks post-fertilization throughout lifespan.
Individuals completely missing fingerprints are extremely rare, but famous for encountering difficulties entering foreign countries. That is why their condition, scientifically termed adermatoglyphia, was surnamed the "immigration delay disease".
In 2007, a 29-year-old Swiss healthy woman complained about recurring trouble at entry to the United States due to identity checks using computerized recognition of fingerprints. Since eight other members of her family also lacked fingerprints, Eli Sprecher and his colleagues hypothesized that the cause of this trouble might be genetic. By comparing the DNA sequence of members of her family having no fingerprints with the DNA sequence of the other members with normal fingerprints, they found a mutation in a gene called SMARCAD1. As reported in their publication in the American Journal of Human Genetics, this gene encodes two isoforms, a long one found in all tissues, and a shorter one specifically expressed in the skin. The described mutation causes aberrant production and decreased stability of the short, skin-specific isoform but leaves the other unaffected, which probably explains the very limited phenotype observed in this family.