Photo Quiz

Linear Hyperpigmentation


Am Fam Physician. 2021 Jun 1;103(11):691-692.

A 26-year-old patient presented to urgent care with a worsening rash on the left forearm that developed four days earlier. The rash started after the patient spent a weekend at the beach. The rash was initially mildly erythematous but became hyperpigmented over the two days before presentation.

The patient had no associated symptoms, including pruritus, pain, fever, and myalgias. No close contacts had similar rashes, and the patient had no recent exposures or travel.

Physical examination revealed a linear hyperpigmented rash on the left forearm, extending from the wrist to the elbow (Figure 1).




Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

  • A. Cellulitis.

  • B. Cutaneous larva migrans.

  • C. Lymphangitis.

  • D. Phytophotodermatitis.

  • E. Superficial thrombophlebitis.


The answer is D: phytophotodermatitis, a phototoxic eruption caused by exposure to furocoumarin compounds in plants and then to sunlight.1 Furocoumarins are found in many plants, including citrus fruits (limes, lemons, oranges, and grapefruits), celery, parsley, carrots, dill, and figs. Most cases of phytophotodermatitis develop after exposure to citrus, often when consuming alcoholic beverages, leading to the nicknames “the other lime disease” and “margarita dermatitis.” On further questioning, the patient recalled making margaritas with fresh limes during the beach weekend and lime juice dripping down the patient's forearm in the pigmented distribution.

Phytophotodermatitis also often occurs in children after playing ou

Address correspondence to Clare L. Coda, MD, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Fitzpatrick JK, Kohlwes J. Lime-induced phytophotodermatitis. J Gen Intern Med. 2018;33(6):975....

2. Nguyen DA, Muhammad MK, Lee GL. Phytophotodermatitis. In: Trevino J, Chen AYY, eds. Dermatological Manual of Outdoor Hazards. Springer; 2020:43–56.

3. Harshman J, Quan Y, Hsiang D. Phytophotodermatitis: rash with many faces. Can Fam Physician. 2017;63(12):938–940.

4. Raff AB, Kroshinsky D. Cellulitis: a review. JAMA. 2016;316(3):325–337.

5. Ma DL, Vano-Galvan S. Images in clinical medicine. Creeping eruption—cutaneous larva migrans. N Engl J Med. 2016;374(14):e16.

6. Ahmed I, Charles-Holmes R. Phytophotodermatitis mimicking superficial lymphangitis. Br J Dermatol. 2000;142(5):1069.

7. Spelman D. Lymphangitis. UpToDate. Updated November 20, 2020. Accessed April 13, 2021.

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

A collection of Photo Quiz published in AFP is available at

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