[Phenotypic features in autistic individuals: the finger length ratio (2D:4D), hair whorl, and hand dominance].

OBJECTIVE

The aim of this study was to compare the finger length ratio (2D:4D), hair whorl direction, and hand, foot, and eye dominance in autistic and healthy individuals, and to investigate the phenotypic characteristics of autism.

MATERIALS AND METHODS

The study included 37 males diagnosed with autistic disorder and 121 healthy males, all aged 4-18 years. The length of the index and ring fingers of both hands--from the proximal bend of the metacarpophalangeal joint to the fingertips--was measured with digital calipers and the index-ring finger (2D:4D) ratio was determined. The distance between hair whorls, their perpendicular distance from the mid-sagittal line, and their direction of rotation were calculated in the autism and control groups. Hand, foot, and eye dominance were determined in both groups. The findings were evaluated using SPSS v.15.0.

RESULTS

The autism group had a greater number of hair whorls than the control group. The distance between hair whorls and the mid-sagittal line was longer in those with left hand and left eye dominance. A significant difference in the 2D:4D ratio of the right and left hands between the 2 groups was not observed.

CONCLUSION

The autism group had more hair whorls than the control group and the hair whorls in the autistic individuals with left hand and left eye dominance were located further from the mid-saggital line. We think that these novel findings might contribute to the determination of the phenotypic features specific to autism.