Background: The Psoriasis Area and Severity Index does not take the severity of nail involvement into account.
Objectives: To devise a system of scoring for nail psoriasis.
Methods: A system of scoring for nail psoriasis was devised that takes into account the site of the pathology, i.e. (i) the matrix, (ii) the subungual tissues distal to the lunula, or (iii) the whole nail unit.
Results: The proposed scoring system evaluates several signs of nail psoriasis separately, each on a 1-3 scale: pitting, Beau's lines, subungual hyperkeratosis and onycholysis.
Conclusions: Using this classification it will be possible to assess and grade nail pathology simply and accurately.