(BMJ)—A 43-yo woman presented w/ a burning rash on her forearms 2 days after trimming parsnips on a sunny day in her garden plot. Exam: red streaks w/ tense blisters on bilateral forearms. What is the dx?
Solar urticaria
Acute intermittent porphyria
Primary cutaneous nocardiosis
Erythema solare
Phytophotodermatitis
You are correct. The linearity of some of the lesions suggested exposure to an external force that contributed to the process. She was diagnosed clinically as having phytophotodermatitis triggered by contact w/ parsnips and exposure to sunlight. Phytophotodermatitis is a phototoxic reaction that occurs after contact w/ plants containing furocoumarins and concomitant or subsequent exposure to ultraviolet light. Commonly implicated plants include parsnips, limes, parsley, celery, figs, and carrots. The initial blistering and erythema resolve w/ marked hyperpigmentation and w/o scarring. This pt's rash improved w/ topical clobetasol.

BMJ 2017;357:j2383