Dermatopathologie [Kennisquiz]

A 24-years old male patient with no medical history visited the Dermatology clinic because of blue lesions located on his right shoulder and lower back. The lesions were not painful or itchy. Skin inspection showed confluent erythematous papules and patches in a linear distribution and with purple and white discoloration. Histopathology revealed a superficial lichenoid inflammation. Diagnosis: Blaschko-linear lichen planus. After successful treatment with a topical steroid only some residual pigmentation remained visible.