ABSTRACT
The nail unit is divided into the nail plate, nail folds, nail bed, hyponychium and free edge of the nail plate. Dermoscopic assessment may be performed with or without interface fluid; ultrasound gel is the ideal interface medium for the nail because of its viscosity as it gels well in the convex surface of the nail plate and free edge of the nail too. Nail involvement is quite common in psoriasis, particularly if arthritis is present. Nail psoriasis is mainly characterized by pitting, onycholysis, subungual hyperkeratosis and splinter haemorrhages. Pits in psoriasis appear as deep and irregular craters with white halo or white spots inside, which histologically correspond to foci of parakeratosis; notably, white structures may be less evident when using ultrasound gel. Dermoscopic examination of both the proximal nailfold and hyponychium may show red dots that are regular and uniform in distribution in psoriatic patients, especially those affected by nail plate/bed changes.
