Limitations of dermoscopy in detecting distal and lateral subungual onychomycosis among patients with severely dystrophic nail psoriasis

Background Onychomycosis among patients with nail psoriasis is being increasingly reported in the literature. When the two conditions coexist in the same nail, it is usually difficult to clinically detect the fungal nail affection. Objective To study the value of dermoscopy in detecting distal and lateral subungual onychomycosis among patients with nail psoriasis. Patients and methods Fifty psoriasis patients with nail changes were subjected to full history and clinical examination, including targeted Nail Psoriasis Severity Index calculation, dermoscopic examination and nail scrapping for fungal culture on Sabouraud dextrose agar, and dermatophyte (DM) test medium. Results Twelve (24%) of the 50 patients recruited showed a positive mycological growth on culture. Nondermatophyte molds and DM were isolated from 16 and 8% of patients, respectively. Nail psoriasis severity was not affected by fungal growth on culture and no significant relation could be detected between culture results and nail dermoscopic findings. Conclusion Specific dermoscopic signs of distal and lateral subungual onychomycosis do not appear to be evident in severely dystrophic psoriatic nails even when culture results show growth for DM and/or nondermatophyte molds.