BACKGROUND Linear cutaneous lupus erythematosus (LCLE) is uncommon and occurs mainly in children and young adults. To our knowledge, only ten cases of LCLE in adults have been previously reported. A case is presented of LCLE of the left arm in a 55-year-old woman. CASE REPORT A 55-year-old Caucasian woman from the Midwestern United States presented with a three-month history of a pruritic linear eruption on the left arm. She had a previous history of methicillin-resistant Staphylococcus aureus (MRSA) infection of the left forearm. She had previously been treated with topical triamcinolone, hydrocortisone cream, hydroxyzine, and two courses of prednisone. Physical examination showed a unilateral and linear erythematous skin lesion of the left arm that contained papules and followed the embryonal developmental epidermal lines of Blaschko. Histopathology of a 4 mm skin punch biopsy showed an interface dermatitis with keratinocyte necrosis and increased dermal mucin. Immunofluorescence of the skin biopsy, including for antinuclear antigen (ANA), was negative. Prednisone treatment reduced the symptoms of pruritis but did not resolve the rash. However, following topical treatment with betamethasone dipropionate cream for between two and three weeks, and the use of sunblock, the skin lesions resolved. CONCLUSIONS This rare case of LCLE in an older adult showed a similar response to treatment as other forms of cutaneous lupus erythematosus, with treatment that included topical steroids and sun protection. Also, this case supports that environmental trigger factors, such as prior infections, might provide insights into the etiology of LCLE.