Unilateral discoid lupus erythematosus at the site of a healed abrasion wound: an illustration of isotopic response

A 35-year-old man presented in February 2010 with a 3-year history of asymptomatic scaly erythema on his right face. Initially, some asymptomatic red-purple, pea-sized papules developed on his right cheek. The papules then increased in number and extended gradually, forming confluent plaques on his right face in 2 years. The skin lesion, however, has been confined to his right face since onset. The patient did not recall any local trauma history but on review of his old medical chart, he had an abrasion wound on the same site of his right face from a car accident, which brought him to our Emergency Department in 1999. He denied any history of photosensitivity or other systemic symptoms. No family history of collagen diseases was noted. He had been treated unsuccessfully with topical corticosteroid ointment and topical Chinese herbal medicine in private clinics before he came to our hospital. On physical examination, erythematous scaly plaques and papules were found on his right face (Figure 1). The following laboratory investigations were within normal limits, including complete blood cell count, erythrocyte sedimentation rate, creatinine, urine analysis, antinuclear antibody, anti-dsDNA, antiribonucleoprotein, anti-Sm, anti-Ro, and anti-La. A skin biopsy was taken from his right cheek. Histological examination revealed epidermal