Palmoplantar Psoriasis: A Clinico-Pathologic Study on a Series of 21 Cases with Emphasis on Differential Diagnosis.

Palmoplantar psoriasis (PP) is a relatively uncommon variant of psoriasis that affects palms and soles, and that frequently shares both clinical and histologic features with chronic eczema, hyperkeratotic hand dermatitis and allergic contact dermatitis. The present study aims to characterize the histologic features of PP on a series of 21 cases. The following morphological features and their distribution were included: parakeratosis, dilated vessels in papillary dermis, psoriasiform acanthosis with elongation of rete ridges, perivascular lymphocytic infiltrate, decrease/loss of granular layer, Munro's microabscesses, spongiform pustules of Kogoj, spongiosis and lymphocytic exocytosis. The main diagnostic clues and histologic differential diagnoses are also discussed.