Premalignant circumscribed palmar hypokeratosis: a new form of circumscribed palmar hypokeratosis? Case report and literature review.

Circumscribed palmoplantar hypokeratosis (CPH) is a recently described dermatosis of unknown origin, of which 46 cases have been published so far. CPH affects predominantly adult women. It presents clinically with a sharply circumscribed annular erythematous depressed plaque rimmed by a slightly hyperkeratotic border, localized usually over the thenar or hypothenar eminences of the palm, less commonly on the soles. Histopathologically, it is characterized by an abrupt decrease in the horny layer thickness, forming a sharp stair between normal and involved skin. We report herein a new patient with CPH who presented an associated aspect of actinic keratosis, a hitherto unreported finding. This case suggests that CPH can undergo malignant transformation, probably as a result of actinic damage. On this occasion, a complete literature review of CPH is presented.