Second-To-Fourth Digit Ratio (2d: 4d) In Rheumatoid Arthritis: A Case-Control Study

INTRODUCTION: Second-to-fourth digit ratio (2D: 4D), the ratio of the second finger length to the fourth finger length, is associated with exposure to prenatal sex steroids. Rheumatoid arthritis (RA) is more common in women, suggesting the effect of hormonal factors. The aim of the present study was to determine whether 2D: 4D, which is associated with sex hormone levels, is affected in RA patients.
METHODS: Digital images of the right and left hands of 205 RA patients (mean age 47.8±11.3 years; 84% female) and 205 age and gender matched healthy controls (mean age 47.3±11.6 years; 84% female) were obtained. 2D: 4D was calculated by dividing the 2nd digit length by the 4th digit length. The 2D: 4D difference between the right and left hand (ΔR-L 2D: 4D) was obtained by subtracting the left hand 2D: 4D ratio from the right hand 2D: 4D ratio.
RESULTS: No difference was found between RA patients and the control group in terms of 2D: 4D ratio in the right and left hand. In female patients with RA, ΔR-L 2D: 4D was higher compared to the control group. For both hands, the 2D: 4D increase rate in women compared to men was higher in RA patients compared to the control groups.
DISCUSSION AND CONCLUSION: The detected 2D: 4D ratio differences suggest that prenatal estrogen/androgen balance may be altered in female patients with RA. According to the best of our knowledge, this is the first study to evaluate 2D: 4D change in patients with RA.