to the editor: The "Photo Quiz"¹ in the January 1, 2005, issue of American Family Physician was a nice quiz about an uncommonly diagnosed condition: lichen nitidus. I would like to add to the discussion of the differential diagnosis. Lichen nitidus is one of only a few skin conditions that exhibit the Koebner phenomenon. Other skin conditions that exhibit the Koebner phenomenon are: juvenile rheumatoid arthritis (systemic form),² lichen planus, molluscum contagiosum, pityriasis lichenoides et varioliformis acuta,³ psoriasis, vitiligo,⁴ and warts.

Asking the patient about areas of trauma, and then looking for clustered or linear distribution of isomorphic lesions may be a major clue in the diagnosis of these disorders.

Thank you for an interesting discussion.