Pityriasis rotunda.
Pityriasis rotunda affects dark-skinned persons and appears as nearly perfectly round or oval scaling patches. Often associated with chronic and debilitating illness or malignant disease, it is probably a localized variant of acquired ichthyosis.
D000368:Aged; D044383:Black People; D005260:Female; D006801:Humans; D010915:Pityriasis / Q000188:drug therapy / Q000473:pathology*; D012867:Skin / Q000473:pathology; D014212:Tretinoin / Q000627:therapeutic use
D014212:Tretinoin