Fingers, Relative Length Of

Clinical Features

Kloepfer (1946) studied the relative length of the index and middle fingers. Short index fingers (i.e., the index finger is shorter than the ring finger) is said to be dominant in men, recessive in women. Three phenotypes were noted--second longer than fourth, second equal to fourth, and second shorter than fourth (Phelps, 1952).

Mapping

Medland et al. (2010) performed a genomewide association study in 1,507 11-year-old children from the Avon Longitudinal Study of Parents and Children (ALSPAC) in whom the ratio of the lengths of the second to fourth digit (2D:4D ratio) had been measured and in a sample of 1,382 12- to 16-year-olds from the Brisbane Adolescent Twin Study. Metaanalysis of the 2 scans identified a single variant in the LIN28B gene that was strongly associated with 2D:4D, rs314277 (p = 4.1 x 10(-8)); the finding was independently replicated in an additional 3,659 children from the ALSPAC cohort (p = 1.53 x 10(-6)). The authors noted that the minor allele of the rs314277 variant had previously been linked to increased height and delayed age at menarche (see 612882), but in the present study it was associated with increased 2D:4D in the direction opposite to that of previous reports. Medland et al. (2010) questioned the validity of 2D:4D as a simplistic retrospective biomarker for prenatal testosterone exposure.