Pityriasis rotunda is an uncommon acquired dermatosis related to a keratinization disorder described first in 1906. This dermatosis was called pityriasis circinata and "pseudo-ichtyose acquise en taches circulaires." It is characterized by hyperpigmented or hypopigmented, sharply defined, circular, or oval scaly plaques of variable size, which develop on the trunk and proximal parts of the limbs. Pityriasis rotunda, not commonly encountered in some regions of the world, is not always easy to diagnose.
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