Hypothenar radial arch in man: observations on its distribution, morphology, symmetry, and inheritance.

Hypothenar radial arch was found in 2.07% of the males and 2.82% of females in a sample of 2,130 Bulgarians. Persons bearing the pattern on the right hand display the highest frequency, followed by those bearing the pattern bilaterally and those with it on the left hand. A well-expressed tendency of the hypothenar radial arch towards symmetrical occurrence was disclosed through the ratio between the actual and expected frequency of its bilateral occurrence. This ratio is recommended as an efficient estimator of tendency toward symmetry. The presence of the pattern is associated with morphological peculiarities of the other dermatoglyphic features of the palm. Line A ends at two parts of the palm periphery which are extremes of its usual distribution. Line D is shortened and the ridges run more vertically than in palms without the pattern. The connection of the hypothenar radial arch with the border ulnar triradius, along with the observations on the opposite hypothenars in the unilateral cases, provides a support of Wilder's conception concerning the mode of formation of the pattern. A genealogical tree exhibiting transmission of the pattern over three consecutive generations is presented. A pattern of dominant inheritance with a fairly reduced penetrance is compatible with the genealogical data.