Differential Diagnosis of Nail Psoriasis and Onychomycoses: A Report Based on 40 Years of Specialised Nail Consultations

Abstract

Ungual psoriasis and onychomycosis are common nail diseases. Despite their different aetiology and course, surprisingly they have much in common both clinically and histopathologically, rendering their distinction often very challenging. Because their treatments are fundamentally different, anti-inflammatory–immunosuppressive for psoriasis and anti-infective for onychomycoses, an exact diagnosis is crucial for their management. Psoriasis is the dermatosis with the most frequent nail involvement. Pits, ivory-coloured spots, salmon or oil spots, subungual hyperkeratosis, onycholysis, and splinter haemorrhages are the most common nail signs. Onychomycoses are thought to be the most frequent nail diseases. This statement is disputed for toenails, for which orthopaedic abnormalities are said to be even more frequent and mimic fungal nail infections.