Clinical features and long-term follow-up of 20 cases of parakeratosis pustulosa.

We report the clinical features and long-term follow-up of 20 pediatric patients with parakeratosis pustulosa (PKP). In eight children PKP was considered as a clinical manifestation of psoriasis. Of these, three children had skin psoriasis at the time of our observation, two developed nail psoriasis, and three developed psoriatic pitting during follow-up. Parakeratosis pustulosa was considered a symptom of allergic contact dermatitis in four patients, whereas atopic dermatitis was possibly responsible for PKP in two patients. A complete recovery from disease was observed in 11 patients. The results of our study suggest that PKP is not a single entity but rather represents a nail symptom that can be produced by several inflammatory diseases, including nail psoriasis, atopic dermatitis, and contact dermatitis.