Border Sharpness Index: A Proof-of-Concept Approach for Quantifying Pigmentary Transition Morphology in Vitiligo

Vitiligo assessment traditionally focuses on lesion extent, depigmentation burden, and disease activity using clinical examination, Wood's lamp evaluation, and scoring systems, such as the Vitiligo Area Scoring Index (VASI) and Vitiligo Disease Activity (VIDA) score. Although lesion border morphology is routinely recognized during clinical evaluation and may contribute to assessments of disease stability, objective quantitative characterization of pigmentary transition morphology remains largely unexplored. We present an exploratory image-analysis approach based on grayscale intensity profiling of Wood's lamp images obtained from a 68-year-old woman with vitiligo affecting both hands. Images were converted to 8-bit grayscale using Fiji/ImageJ, and linear intensity profiles were generated across representative lesional borders, healthy skin, and intralesional depigmented areas. To objectively quantify pigmentary transition morphology, we propose an exploratory Border Sharpness Index (BSI) integrating grayscale intensity variation and transition distance. Border-crossing profiles demonstrated reproducible directional intensity transitions that differed from both healthy skin and intralesional control tracings. Healthy skin exhibited minimal physiologic fluctuation, whereas intralesional tracings showed local oscillatory variation without organized directional transition patterns. These findings suggest that grayscale intensity profiling can objectively characterize the spatial architecture of the pigmentary transition zone using standard digital images and freely available image-analysis software. The proposed BSI represents one possible quantitative descriptor of pigmentary transition morphology, integrating morphometric and colorimetric information. While exploratory and nonvalidated, this proof-of-concept methodology introduces a previously underexplored quantitative dimension of vitiligo assessment focused on the spatial architecture of the pigmentary transition zone rather than lesion extent or disease activity alone. Further studies are needed to evaluate reproducibility, clinical correlation, and potential applications in the assessment of lesion stability and therapeutic response.