Question
A healthy 69-year-old man with osteoarthritis of the knees presented with a 2-week history of darkening of the skin on the left thigh. On examination, there was a reddish-brown, pruritic, nontender, macular, nonblanching discoloration around the medial aspect of his left knee, with a few superficial erosions. He had no fever, chills, or other constitutional symptoms. For several weeks before this event, the patient had applied a heating pad repeatedly to his left knee to relieve the discomfort from the osteoarthritis.
What is the diagnosis?
Acanthosis nigricans
Erythema ab igne
Lymphangitis
Mycosis fungoides
Livedo reticularis
Created by USMLE PlAB MCQ
