Mapping in healthy subjects different body areas for dermal thickness and skin hardness by high frequency ultrasound and durometry.

Objectives: Body mapping of normal values of skin thickness and hardness may be a useful aid in daily practice. By employing non-invasive techniques, our pilot study provides these values in healthy individuals using high frequency ultrasound (HFUS) and durometry in areas used to evaluate the modified Rodnan skin score (mRSS).

Methods: One-hundred-fifty-two healthy volunteers from Ghent and Genova University Hospitals (mean ages 31.2, 35.5, and 64.9 years), were evaluated to exclude rheumatologic diseases. HFUS and durometry were used to assess the dermal status in mRSS areas. Exploratory analyses were performed to assess the impact of demographic and anthropometric characteristics on intra-subject skin measurements. Statistical analysis was performed with Datatab®.

Results: The upper and lower arms exhibited significantly higher durometry values and lower dermal thickness compared to the trunk regions, underscoring distinct variations across these areas (all p<0.05). The hardest skin was found on the finger, while the thickest dermal measurements were at the abdomen and thighs. Dermal thickness was higher in men in multiple areas in the three cohorts, albeit with relatively modest effect sizes (r coefficients ranging between 0.02 and 0.6). Despite the presence of significant inter-group differences in dermal thickness, HFUS mapping showed similar topographical distributions in both centres.

Conclusions: Our study offers a comprehensive skin mapping status in healthy individuals. Key findings indicate lower dermal thickness in the upper arms, legs, and feet, and higher skin hardness in peripheral areas like fingers, compared to truncal regions.This skin mapping pilot study might provide the normal distribution values in outpatient clinics for physicians to be used when comparing the same areas in pathological conditions like systemic sclerosis-related fibrotic skin.