A 20-year-old man presented with a six-month history of inflamed bumps and what appeared to be focal bruising on his legs, thighs, and arms that left persistent hyperpigmentation after resolution. The rash had been exacerbated by heat exposure and appeared worse at night. He had joint pain and paresthesia but no photosensitivity, malar rash, alopecia, or mouth ulcers. When he consulted a rheumatologist, he had an elevated antinuclear antibody titer of 1:160. The patient was taking aspirin and acetaminophen and using a topical diclofenac sodium solution. He had no relevant family, medical, or social history. He did not abuse alcohol.

Physical examination revealed faint, dark purple, hyperpigmented patches in a reticular pattern, forming several complete rings on his dorsal thighs and a few on his lower legs and arms (Figure 1).

Question

Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

• A. Cutaneous polyarteritis nodosa.

• B. Drug hypersensitivity reaction.

• C. Takayasu arteritis.

• D. Urticarial vasculitis.