Several months ago, this 7-year-old girl noticed a lesion on her outer vagina. In addition to growing larger, the lesion has begun to itch.
The patient’s mother has attempted treatment with anti-yeast cream and 1% hydrocortisone cream; neither has helped.
Both mother and daughter deny any recent trauma to the area, presence of similar lesions, or family history of skin disease or arthritis.
The child is well in all other respects; she takes no medications and has no history of serious illnesses or surgeries.
A solitary, 8- x 2-cm, salmon-pink plaque covered with uniform tenacious white scale is located on the left labia majora in a vertical orientation. The margins are sharply defined. There is no tenderness or increased warmth on palpation.
No similar changes are seen on the elbows, knees, scalp, trunk, or nails.
A biopsy of the lesion is performed. The pathology report shows parakeratosis and elongation of rete ridges.
What is the diagnosis?