Abnormal dermatoglyphics in absence of thumb.

Dermatoglyphics of six patients with absence of thumb are described. Two specific abnormal configurations were seen in the palmar area. In the first, there was no axial triradius and the course of the ridges in the proximal part of the palm was transversal. In the second, a peculiar distal loop on the radial border was present with a palmar triradius. These abnormal patterns are probably due to the absence of a thenar volar pad or the presence of an abnormal one when the ridges are formed.