Dermatoglyphics, also referred to as epidermal ridges, are the distinct patterns and lines on the hands and fingers. These ridges appear on the hands between weeks 6 and 15 during foetal development, and remain largely unchanged after this period. Alterations in the patterns and counts of dermatoglyphics may be an indication of disruption to foetal development in the early- to mid-gestation period. A triradius occurs where three ridge systems meet at a point, and occurs four times on the palm, at the base of each of the four digits (a, b, c, and d). Dermatoglyphic indices include: fingertip patterns; finger ridge counts, which are the number of ridges between the center of the fingertip patterns and their corresponding triradius; palmar ridge counts, which are the number of ridges on the palm connecting two triradii; fluctuating asymmetries, which are the differences in ridge counts or pattern types between parallel structures on the left and right hands; and the ATD angle, which is the angle formed by lines drawn from the most remote triradius near the base of the palm, to triradii a and d, located close to the index and little fingers respectively.

What is the evidence for dermatoglyphics?

Moderate to high quality evidence found a medium-sized effect of reduced total ridge count and a-b palmar ridge count in people with schizophrenia compared to controls, with no differences in ATD angle, fingertip pattern asymmetry or ridge count asymmetry.

February 2022

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