Analysis of the Intra-Nail Location of Nail Psoriasis

Although nail psoriasis is a common manifestation among patients with psoriasis, large-scale research exploring the association between nail psoriasis lesions and their intra-nail locations has not been conducted. This study is necessary to elucidate the shared pathophysiology among various phenotypes of nail psoriasis.

We aimed to understand the association between nail psoriasis lesions and analyze their intra-nail locations.

We obtained a total of 5,602 cropped fingernail images from 636 patients with psoriasis. We employed the Computer Vision Annotation Tool to annotate the intra-nail locations of nail psoriasis lesions. We computed χ² statistic to examine the relationship between nail psoriasis lesions and conducted an analysis of their intra-nail locations.

Based on the number of lesions, nail pitting was the most common, followed by leukonychia, with the red spots in the lunula being the rarest. We elucidated the associations between different nail psoriasis lesions, pinpointing a significant association between onycholysis and oil spots (χ² statistic=1,623.88), followed by onycholysis-subungual hyperkeratosis (1,607.50), and subungual hyperkeratosis-oil spots (985.76). A spatial relationship was observed between onycholysis and oil spots, with the intra-nail location of onycholysis being more distal compared to the nearest oil spots. A distribution pattern of nail psoriasis was also demonstrated, where nail matrix lesions were primarily located at the center of the nail, and nail bed lesions were predominantly located near the lateral nail folds.

This study represents a pioneering analysis of the intra-nail location of nail psoriasis lesions, revealing substantial associations and spatial relationships between different lesions.