Dermatoglyphics--Arch On Any Digit

Description

Dermal ridge patterns are the result of the interaction of 2 embryologic processes: the formation and later regression of the volar pads between the eighth and twelfth week of gestation and dermal ridge differentiation at around the twelfth week of gestation. The size and shape of the volar pad at the time of ridge differentiation influences the ultimate ridge pattern: in general, if the pad is large, a whorl will be formed, whereas if the pad is small, a plain arch will be formed. A loop is an intermediate pattern. In Caucasians, the loop is the most common pattern, and the arch is a rare pattern comprising 4 to 5% of fingertip patterns in the population. Fingertip arches are more common in females than males (Reed et al, 2006).

Inheritance

Anderson et al. (1979) found evidence of autosomal dominant major gene inheritance with almost complete penetrance for inheritance of fingertip arch patterns in restudy of a large Habbanite kindred studied previously by Slatis et al. (see 125590). Furthermore, analysis suggested linkage to the haptoglobin locus (lod 1.315 at theta about 0.15) and excluded linkage with blood group P1 and Rhesus. The possible haptoglobin linkage is of special interest because of the suggested linkage of another dermatoglyphic syndrome ('ridges-off-the-end'; 125550) with haptoglobin. In addition, Froehlich (1976) found a haptoglobin-ridge count association in 2 apparently unrelated Melanesian populations.

Reed et al. (2006) analyzed 2,484 twin pairs for the presence of at least 1 fingertip simple arch pattern. The frequency of arches in the entire sample was 4.3%: 5.5% in females and 3.2% in males. There were 267 twin pairs concordant for the presence of an arch on any finger, yielding a heritability of 91% for the trait. Reed et al. (2006) concluded that a genetic locus or loci are responsible for the simple arch pattern.