In polyarteritis nodosa, which description of the skin rash is most characteristic?

• A. Diffuse maculopapular
• B. Mottled, lace-like purple discoloration
• C. Palpable purpura
• D. Violaceous, raised discoloration

Answer: (B)

In polyarteritis nodosa, the skin finding that is most characteristic is livedo reticularis—a mottled, lace-like purple discoloration that forms a net pattern over the skin. This happens because inflammation and thrombosis affect medium-sized arteries supplying the skin, causing uneven blood flow and ischemia that creates the distinctive net-like change. This pattern is more specific to PAN than other rash descriptions. A diffuse maculopapular rash is nonspecific and common in many conditions. Palpable purpura points to small-vessel vasculitis, not the medium-vessel involvement seen in PAN. Violaceous, raised discoloration suggests nodules or plaques rather than the characteristic reticular pattern. So the mottled, lace-like discoloration best fits PAN’s typical cutaneous presentation.