Abstract: 【Abstract】 Objective To evaluate and compare dermoscopic features of toenail psoriasis and fingernail psoriasis. Methods Between June 2020 and January 2022, 61 patients with confirmed toenail psoriasis and 80 with confirmed fingernail psoriasis were enrolled from the Department of Dermatology of Peking University First Hospital. Dermoscopy was performed on 139 affected toenails and 158 affected fingernails among the psoriasis patients, and dermoscopic characteristics were analyzed between the two groups by using the chi-square test. Results The most common dermoscopic feature of nail psoriasis was pitting （223/297, 75.08%）, followed by splinter haemorrhages （164/297, 55.22%）, subungual hyperkeratosis （133/297, 44.78%）, oil drop sign（126/297, 42.42%）, complete onycholysis （121/297, 40.74%）, linear margin of the proximal onycholysis （107/297, 36.03%） and linear erythema at the margin of the onycholysis （77/297, 25.93%）. Compared with the patients with fingernail psoriasis, those with toenail psoriasis more commonly presented with subungual hyperkeratosis （81［58.27%］ vs. 52［32.91%］, P < 0.001）, punctate/ blocky haemorrhages （22［15.83%］ vs. 11［6.96%］, P < 0.05）, longitudinal striae （34［24.46%］ vs. 10［6.33%］, P < 0.001）, longitudinal nail splitting （24［17.27%］ vs. 9［5.70%］, P < 0.01）, brown discoloration （14［10.07%］ vs. 2［1.27%］, P < 0.01）, transverse grooves （17［12.23%］vs. 1［0.63%］, P < 0.001）and leukonychia （10［7.19%］ vs. 1［0.63%］, P < 0.01）; compared with the patients with toenail psoriasis, those with fingernail psoriasis more commonly presented with splinter haemorrhages （100［63.29%］ vs. 64［46.04%］, P < 0.01）, oil drop sign （81［51.27%］ vs. 45［32.37%］, P < 0.01）, linear erythema at the margin of the onycholysis （55［34.81%］ vs. 22［15.83%］, P < 0.001）, partial onycholysis （50 ［31.65%］ vs. 19［13.67%］, P < 0.001）and red spots in the lunula （36［22.78%］ vs. 12［8.63%］, P < 0.01）. Conclusion The dermoscopic features of toenail psoriasis were quite different from those of fingernail psoriasis, and features such as subungual hyperkeratosis, longitudinal streaks, and brown discoloration were more commonly presented in patients with toenail psoriasis.

Key words: Psoriasis, Nails, Nail psoriasis, Dermatoscopic features, Diagnosis