Case 87

A 9-year-old boy presented to the dermatology clinic with a brown streak on his right arm and forehead. The streak on his right arm is shown in Image 87 and was thought to be a ‘whip mark’ and child abuse was suspected. The family reported no history of trauma. The child was at a picnic recently and they did not recall him falling or injuring himself. The child made no disclosures of physical abuse. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429170423/e1d751c1-a9c7-4bb9-9d59-53742c84031a/content/fig87.jpg"/>

What is your diagnosis?

How is the diagnosis made?

What is the treatment?

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The diagnosis of this child’s lesion is lime-induced phytophotodermatitis. The child gave the history of lime juice spilling down his upper arm leaving a serpiginous trail while at the picnic. Plant-induced photosensitivity reactions are the most common phototoxic rashes seen in children. ^{1 , 2} Citrus fruit, especially lemon and limes, parsnips, carrots, dill, parsley, figs and celery (among others) contain furocoumarin, a phototoxic agent. This rash is activated by ultraviolet radiation (UVA), which has a reaction wavelength that can penetrate window glass. The reaction begins the day after the exposure and ranges from mild redness to severe blistering. Post-inflammatory hyperpigmentation is a common sequela as in this child.

The diagnosis is made by recognizing the splash, spread or drip patterns made by external agents against the skin. When this is followed by sun exposure, the plant psoralens (furocoumarin) are activated. It is important to recognize this condition as it may be confused with child abuse. ^{3 , 4} A biopsy would show only inflamed or pigmented skin but will not give us clues to the cause. One can verify the diagnosis with photo patch testing but this is cumbersome and rarely needed in these cases of phytophotodermatitis.

Treatment with topical steroids may be needed if the area is red and itchy. In cases where the patient is concerned about the hyperpigmented skin, bleaching creams may be used. Patients are advised to avoid contact with the triggering plant together with sunlight.