A 61-year-old white man presented with a 2-year history of linear pigmentation involving his third right fingernail. There was no history of trauma. Physical examination revealed that approximately 90% of the nail plate was involved, with several 0.5- to 2.0-mm homogeneous, brown-black, longitudinal, pigmented streaks and intervening red hues (Figure 1). There were no palpable nail plate changes. Periungual pigmentation was not evident. Lymphadenopathy was not present, and there was no other significant physical finding.
Smith DF, Morgan MB, Bettencourt MS. Longitudinal Melanonychia—Quiz Case. Arch Dermatol. 2003;139(9):1209-1214. doi:10.1001/archderm.139.9.1209-a