What could cause this pigmentation on her wrist?

This 47-year-old female presented for evaluation of an asymptomatic pigmented eruption on her volar right wrist of only a 4 week duration. She denies any new exposure history.

What could be the cause?

A.Phytophotodermatitis.

B.Contact dermatitis.

C.Lichen planus.

D.Lichen striatus. 

E.Herpes zoster.

(Answer and discussion on next page)

Answer: Phytophotodermatitis

Phytophotodermatitis is a cutaneous phototoxic inflammatory eruption resulting from contact with light-sensitizing botanical substances and long-wave ultraviolet (UV-A 320-380 nm) radiation. The eruption usually begins approximately 24 hours after exposure and peaks at 48-72 hours. Causes typically include Queen Anne’s lace, parsnip, celery, lime and fig.

On further questioning, the patient admitted remembering squeezing lime in her drink at a lake the weekend it appeared. 

Contact dermatitis (choice B) would be itchy with more erythema; lichen planus (choice C) would typically be itchy with flat purple papules; lichen striatus (choice D) would be more extensive with lichenoid flat papules in a band on the arm; and herpes zoster (choice E) would be tender grouped vesicles. ■