Focal porokeratosis of nuchae: case report.

Porokeratosis is the common name of several diseases of unknown pathogenesis, which are similar in clinical appearance. It was first described in 1893 and was thought to be a disorder of sweat glands, hence the name porokeratosis. The lesion that can be found in all cases is annular, with atrophic center, and hyperkeratotic outer ring. Cases of porokeratosis have been linked with genetic heritage, excessive ultraviolet exposure, kidney failure, and state of immunosuppression, but no definitive link has been established. As a rare condition, its main feature is that the correct diagnosis can be delayed for a significant period of time. Porokeratotic lesions have a high incidence of malignant transformation and are considered premalignant. We present a case where a porokeratotic lesion was unsuccessfully treated as a psoriatic lesion for more than a year in a patient with previously diagnosed psoriasis. A skin biopsy was performed at our department, which revealed classic cornoid lamella and thus led to the correct diagnosis. The lesion was excised. Additional diagnostic tests revealed normal kidney function and intact immune system. A follow-up protocol was established for the patient, ensuring timely diagnosis of any future porokeratotic lesions. Porokeratosis, especially when there are only few lesions, is not difficult to manage - once it is diagnosed. A diagnosis of porokeratosis may also aid in identifying a serious systemic disease such as kidney failure. Importantly, a misdiagnosis of porokeratosis may lead to development of skin cancer.