Comparison of dermoscopic characteristics on toenail onychomycosis in psoriatic and non-psoriatic patients: A prospective study

Background: Psoriatic patients may experience the coexistence of onychomycosis (OM). However, the evaluation of OM in psoriatics has been hindered by potential clinical differences from OM in non-psoriatics. Objective: To assess and compare dermoscopic features between toenail OM in psoriatic and in non-psoriatic patients. Patients and Methods: Between September 2020 and September 2023, dermoscopy was conducted on 183 affected toenails by OM in psoriatics and 232 affected toenails by OM in non-psoriatics in two centres. The dermoscopic characteristics were compared using the Chi-squared test. Results: Among toenail OM cases in psoriatic subjects, the most prevalent dermoscopic features included pitting (147/183, 80.33%) and subungual hyperkeratosis (118/183, 64.48%). Conversely, toenail OM in non-psoriatics was characterized by subungual hyperkeratosis (175/232, 75.43%) and nail spikes (139/232, 59.91%). Comparative analysis revealed a significantly higher occurrence of pitting (80.33% vs. 15.96%, p < .001), periungual telangiectasis (22.40% vs. 4.74%, p < .001), oil patches (12.57% vs. 0.43%,p < .001) and transverse grooves (43.72% vs. 28.45%,p < .01) in toenail OM in psoriatics. Furthermore, toenail OM in psoriatics exhibited a significantly lower frequency of yellow structureless area (13.11% vs. 42.67%, p < .001), nail spikes (43.17% vs. 59.91%, p < .01), ruin appearance of sulphur nugget (8.20% vs. 31.03%, p < .001), dotted/blocky haemorrhage (6.01% vs. 20.69%,p < .001) and partial onycholysis (32.79% vs. 46.98%, p < .01). Conclusions: Dermoscopic features of toenail OM in psoriatic and non-psoriatic patients exhibit notable differences. OM in psoriatics shows a higher frequency of pitting and periungual telangiectasis, while a lower frequency of yellow structureless areas and nail spikes under dermoscopy.