Abstract

Macular lymphocytic arteritis (MLA) is a rare cutaneous medium-vessel vasculitis which presents on the lower extremities as macules, papules, or livedoid patches. MLA has been described as having a benign, yet persistent course without documented progression to systemic vasculitis. Histologically, a medium-vessel lymphocytic vasculitis is present without neutrophils. The exact etiology of MLA remains unknown; however, some postulate that it may lie on a spectrum with its important differential diagnosis, polyarteritis nodosa (PAN). Treatment strategies to date have included immunosuppression and/or supportive care. We present a case of a 54-year-old man with a history of well-controlled HIV and hepatitis C who presented with scattered hyperpigmented macules and small patches on the back and bilateral lower extremities. The lesions were non-pruritic, slowly progressive over a period of six months, and without associated scale. Histopathologic evaluation demonstrated basal melanosis with hyperkeratosis, dermal sclerosis and deep dermal perivascular lymphocytic inflammation. Foci of fibrinoid necrosis of vessel walls with intraluminal lymphocytes, minimal karyorrhectic debris and prominent concentric fibrosis were present. Immunostaining with CD3 highlighted many intraluminal lymphocytes, while MPO was negative for intact neutrophils. Additionally, Fontana-Masson highlighted basal melanosis without pigment incontinence. In light of the clinical, histomorphologic and immunophenotypic findings, a diagnosis of MLA was rendered. We aim to increase awareness of this rare entity while highlighting key diagnostic features.

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