Nummular Eczema Discoid Coin-Shaped

A 62-year-old retired male farmer presents in winter with a six-week history of intensely pruritic lesions that worsen at night and after hot showers. He has a long-standing history of dry skin and occasional alcohol excess. On examination, he has multiple sharply demarcated lesions scattered symmetrically on the extensor surfaces of the forearms, dorsa of the hands, and pretibial shins. KOH mount is negative for hyphae. Skin biopsy shows spongiosis with intraepidermal vesiculation and superficial perivascular lymphocytic infiltrate. The structure marked **A** in the diagram represents the clinical presentation most consistent with which diagnosis?