Linear porokeratosis on the hand of a 51 year old woman. Porokeratosis is a condition characterised by circular lesions on the skin. The lesions grow slowly, and in some cases may turn cancerous. For this reason biopsies need to be taken, especially if a lump develops in the affected area. The condition is hereditary, although it may also be brought on by exposure to ultraviolet radiation, or arise after immunosuppression. There is no cure for the condition, but it does not cause symptoms in most cases.