Laboratory Studies
Phytophotodermatitis (PPD) is a clinical diagnosis. No serum level assay for psoralens is available or appropriate. Clinical presentation is delayed, and systemic clearance of psoralens is complete. Laboratory data (eg, porphyrin levels) may be obtained to exclude other diagnoses.
Other Tests
With yeast inhibition technique, plant extract is used to evaluate for presence of psoralens.
In individuals in whom the diagnosis is in question, referral to a dermatologist for photopatch testing may be warranted. Testing should include pesticides and plant allergens.
Procedures
In individuals in whom the diagnosis is in question, referral to a dermatologist for a skin biopsy may be warranted. A skin biopsy may demonstrate epidermal hyperkeratosis, necrotic keratinocytes, "sunburn cells," epidermis spongiosus, and an inflammatory cell infiltrate. An increase in melanocytes is seen. [34]
A photopatch test may be useful if the clinical picture does not clearly suggest phototoxicity rather than photoallergy. [35]
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A 37-year-old white woman presented to the clinic complaining of a rash on the medial part of her right thigh and left arm that was acquired after clearing some weeds in her yard. A phototoxic combination of sunlight and a psoralen-containing plant produced this bizarre linear vesicular eruption.
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Closer clinical view of bizarre angulated vesicular streaks, which occurred after contact with a plant and ultraviolet light exposure.
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A 26-year-old female airline flight attendant exposed to lime while serving drinks en route to the Caribbean. During the Caribbean layover, she had significant sun exposure. The combination of lime juice and sun exposure led to a drip-pattern blister formation on the dorsal forearm consistent with phytophotodermatitis. This picture clearly delineates the potential severity of phytophotodermatitis with extensive blister formation.
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The 2-month follow-up photo of the patient above demonstrates the potential postinflammatory pigmentation changes and scarring that may occur with severe blistering of phytophotodermatitis.
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Close-up view of vesicular linear streaks with morphology suggestive of scattered foci of epidermal necrosis.
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Queen Anne's lace, a member of the Umbelliferae family of plants, is well known to produce a furocoumarin-induced phototoxic eruption.
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Ficus. The common fig contains furocoumarins and should be considered amidst the list of potential offending agents that cause phytophotodermatitis.
