Curvilinear violaceous plaques along Blaschko lines

A 29-year-old man was referred to dermatology with a 5-year history of violaceous crusted plaques with white central regions of ulcerations and overlying erythema that extended in a curvilinear fashion from the right side of his upper back, shoulder, and upper portion of the right arm along the Blaschko lines (Fig 1). He denied any pain, pruritus, or bleeding. His medical and family histories were unremarkable. The laboratory workup, which included a complete blood count, blood urea nitrogen, urinalysis, liver function test, and antinuclear antibodies, was within normal limits.