Case for diagnosis

Ostraceous psoriasis is a rare form of psoriasis,characterized by lesions with firmly adhered thick scales,in various colors,with surfaces resembling oysters shells. the protracted course of clinical presentation allied with peculiar lesions and histopathological examination permit the diagnosis. lesions are usually resistant to topical medications,requiring systemic treatment. it is important that dermatologists are able to diagnose the unusual forms of psoriasis to avoid iatrogeny. we report the case of a patient with ostraceous psoriasis treated with methotrexate. © 2014 by anais brasileiros de dermatologia.