Is There an Association Between Male Alopecia Areata and the Ratio of Second to Fourth Finger Length?

Aim: The ratio between the lengths of the second and fourth fingers (2D to 4D) has been shown to indicate exposure to androgens prenatally. Although an association between alopecia areata (AA) and androgenic hormones has been recently suggested, the 2D to 4D ratio of AA has not yet been investigated. We aimed to investigate the lengths of the 2D to 4D in males with AA, as well as the potential links between 2D to 4D ratios and both AA and disease severity. Materials and Methods: Male patients with AA and healthy volunteers participated in the study. A digital Vernier caliper was employed to measure the lengths of the fingers. The severity of alopecia tool and AA severity index were used to calculate the severity of AA. Results: A total of 168 participants were recruited for the study. Compared with healthy controls, the 2D to 4D ratio was significantly lower in both hands of the patients (P P = 0.001 for the right hand and P < 0.05 for the left hand). The right-hand 2D to 4D ratio showed better predictive capacity for AA development than the left hand (area under the curve: 0.952 vs. 0.638). The 2D to 4D ratio of patients and disease severity scores were not significantly correlated (P P > 0.05). Conclusion: To our knowledge, this is the first report to investigate the association between the 2D to 4D ratio and AA. The results of our research suggest that the 2D to 4D ratio of fingers is a possible predictor of AA development.