"Macular arteritis": a latent form of cutaneous polyarteritis nodosa?

Recently described macular arteritis presents as asymptomatic hyperpigmented macules, runs a chronic, indolent course, and shows lymphocytic arteritis at various stages of evolution ranging from fibrinoid necrosis to endarteritis obliterans. Herein, we present another case that was clinically suspected to be unilateral plantar pompholyx. A 47-year-old male presented with a 2-month history of persistent, reticulated, asymptomatic, nonblanching erythematous and brawny macules, and scattered, slightly scaly papules over the plantar instep of his left foot. Two punch biopsies extending to the subcutis revealed healed arteritis (endarteritis obliterans with fragmented elastic lamina) in the subcutis in one biopsy and purpura and hemosiderin deposition surrounding small subcutaneous arterioles and venules in the second. Additional histologic features included lymphocytic eccrine hidradenitis and chronic spongiotic dermatitis. Extensive laboratory work did not reveal evidence of systemic disease. Despite topical corticosteroid therapy, he has had persistent, asymptomatic disease after 6 months follow-up. The differential diagnoses considered included pigmented purpuric dermatitis, perniosis (chilblains), plantar eccrine hidradenitis, Buerger disease, livedo vasculopathy, and cutaneous polyarteritis nodosa. Cutaneous polyarteritis nodosa also runs a benign course and is denoted by muscular vessel vasculitis, which can resolve with retiform hyperpigmentation. Based on these overlapping clinical-pathologic features, macular arteritis might represent a latent, non-nodule forming chronic variant of cutaneous polyarteritis nodosa.