Lichen striatus in an adult following trauma.

A 36-year-old man presented with a linear erythematous eruption along his right forearm and dystrophy of his right thumbnail. These changes had developed 2 weeks after his right thumb had been pricked by a pineapple leaf and evolved over a 6-week period. Histopathology revealed features consistent with lichen striatus. He complained of mild intermittent pruritus, which responded to moderate-potency topical corticosteroids. At 12 months the skin eruption had improved, but the nail changes persisted.