A case report on late onset linear discoid lupus erythematosus on the face mimicking linear morphoea

50-year-old female with no known comorbidities presented to the dermatology OPD with complaints of slowly progressive asymptomatic skin coloured linear atrophic plaque over left side of face since, 5 years. Cutaneous examination revealed well demarcated, linear atrophic plaque with hidebound skin over left side of face extending from scalp margin to tip of the nose, involving the lateral wall of nose along the lines of Blaschko. Dermoscopic examination showed structureless areas and loss of follicles as well as eccrine openings. Laboratory investigations including ANA-IFA were negative. A clinical diagnosis of linear morphoea (En- coup de sabre) was made. Further investigation with punch biopsy was performed from the lesion site which gave a histopathological diagnosis of Discoid Lupus Erythematosus and was confirmed with direct immunofluorescence study. Full physical examination, review of systems and laboratory workup showed no features to suggest systemic lupus. She was managed with hydroxychloroquine and sun protective measures. Linear discoid lupus erythematosus can clinically mimic linear morphoea, but histopathological examination provides distinctive features that aid in accurate diagnosis and differentiation between the two conditions. This case gave us valuable insight into keeping DLE as a differential for linear morphoea on the face.