A 28-year-old man with an asymptomatic firm plaque on his right shin: what is your diagnosis?

A 28-year-old man referred to the dermatology clinic with an asymptomatic firm, well demarcated violaceous plaque with bumpy surface on his right medial upper shin since two years ago. At first, the lesion was an erythematous patch and gradually became like a plaque. He had pain and sensation of heaviness in his leg (Figure 1). He had no other skin lesions and was otherwise healthy. There was no family history of the same skin lesion. There were no clinically significant abnormalities in laboratory evaluation. The result of serum screening for antinuclear antibodies (ANA) by ELISA was negative. The color Doppler sonography of the right leg demonstrated multiple varicose veins in the medial aspect of the right leg draining into the distal part of the right greater saphenous vein and incompetency of the right saphenofemoral junction. A punch biopsy was performed on the plaque.