An adolescent girl presented with a 5-year history of asymptomatic, unilateral brown patches involving the right arm, flank, and leg. She had previously been diagnosed as having morphea and had undergone long-term treatment with glucocorticoids without benefit. There was no other medical or family history of skin disease. Physical examination revealed brown, atrophic patches on the right arm, right side of the trunk, and right leg following Blaschko lines (Figure). There was no associated erythema or sclerotic change. Results of laboratory investigations, including a complete blood cell count and liver and renal function studies, were unremarkable. A lesional skin biopsy specimen was obtained from the right arm, which revealed basket-weave hyperkeratosis, mild atrophy of the spinous layer, hyperpigmentation of the basal layer, and a superficial perivascular infiltrate without thickened collagen bundles in the dermis. Based on the clinical and histopathologic features, a diagnosis of linear atrophoderma of Moulin (LAM) was made.