Palmoplantar orthokeratotic filiform hyperkeratosis in a patient with associated Darier's disease. Classification of filiform hyperkeratosis.

We present here the third published case of palmoplantar orthokeratotic filiform hyperkeratosis of particular clinical interest because of associated Darier's disease. We propose a classification of filiform hyperkeratosis in three groups on the basis of the topography (i.e. palmar and plantar, disseminated with palmoplantar sparing and linear) and the histology (i.e. porokeratosis or orthokeratosis) of the lesions. This keratinization disorder does not seem to be a specific disease entity but rather a syndrome secondary to various disorders.