A heritable disorder of faulty keratinization characterized by the proliferation of abnormal clones of keratinocytes and lesions showing varying atrophic patches surrounded by an elevated, keratotic border. These keratotic lesions can progress to overt cutaneous neoplasm. Several clinical variants are recognized, including porokeratosis of Mibelli, linear porokeratosis, disseminated superficial actinic porokeratosis, palmoplantar porokeratosis, and punctate porokeratosis.