Multicentric Bowen disease in linear porokeratosis.

Linear porokeratosis is a genodermatosis, caused by a clonal proliferation of keratinocytes along the lines of Blaschko. This type of porokeratosis is particularly susceptible to malignant degeneration e.g. to Bowen disease, a squamous cell carcinoma (SCC) in situ with the potential for significant lateral spread. Here we report a case of linear porokeratosis on the left leg of a 56-year-old man, complicated with two lesions of multicentric Bowen disease.