people, photosensitivity should be suspected if redness, swelling, itch, or other rash occurs after only limited sun exposure A distinct distribution of skin lesions in sun-exposed areas, such as the face, neck, upper chest, and distal arms and hands, is suggestive of a photodermatosis However, the upper eyelids, postauricular and submental areas, neck folds, and volar wrists are relatively spared, as these areas are often shielded from the sun Many photodermatoses exist, and patient history and physical examination are highly important in making a specific diagnosis Skin biopsy is often nondiagnostic, but other testing such as phototesting or laboratory investigations may be helpful This chapter highlights two of the most common photodermatoses in children, polymorphous light eruption (PMLE) and phytophotodermatitis Polymorphous Light Eruption PMLE is an immune-mediated disorder triggered by ultraviolet light exposure It is more common in young women living in temperate climates and usually occurs in the spring or early summer or after sudden sun exposure during the winter (e.g sunny vacation) Lesions appear within to days after sun exposure and consist of papules, plaques, and vesicles that may be urticarial or eczematous in appearance ( Fig 65.7 ) Erythema multiforme-like lesions have also been reported The face, neck, and sunexposed areas of the arms and hands are most commonly affected Itching or pain is often present The eruption generally self-resolves within weeks if sun exposure is subsequently avoided or reduced The risk of recurrence also decreases during the remainder of the spring or summer as the skin “hardens” with continued ultraviolet light exposure However, PMLE tends to flare at the same time each year, as the skin becomes reexposed to sunlight in early spring or summer Since some patients with systemic lupus erythematosus can have PMLE-like lesions, it is important to ask about other associated symptoms and consider serologic testing FIGURE 65.7 Polymorphous light eruption on the dorsal forearms and hands (From Gru AA, Wick M Pediatric Dermatopathology and Dermatology 1st ed Philadelphia, PA: Wolters Kluwer; 2018.) Juvenile spring eruption is a variant of PMLE that is also triggered by ultraviolet light exposure and usually occurs in the spring It is characterized by edematous papules or vesicles on the helices of the ears The neck, hands, and other sun-exposed areas may also be affected In contrast to PMLE, juvenile spring eruption most commonly affects preadolescent boys Treatment for PMLE consists of symptomatic management with midpotency topical steroids Oral corticosteroids may be considered for very severe symptoms Affected children should be counseled to practice sun protective measures, such as broad-spectrum sunscreen use, prior to and during sun exposure In severe cases, referral to dermatology is indicated for consideration of other preventative therapies Phytophotodermatitis Phytophotodermatitis is a plant-induced phototoxic reaction that occurs in the setting of ultraviolet light exposure after topical contact with or oral ingestion of a photosensitizer Unlike allergic contact dermatitis due to plants (e.g., poison ivy dermatitis) which is caused by type IV hypersensitivity, phytophotodermatitis is a nonimmunologically mediated reaction caused by a photosensitizer followed by ultraviolet light exposure Most commonly, phytophotodermatitis is caused by furocoumarins, which are photosensitizing compounds that naturally occur in certain plants and foods, such as limes, lemons, figs, and hogweed ( Table 65.4 ) Within to hours after contact with furocoumarins, the skin becomes very sensitive to ultraviolet light Subsequent sun exposure leads to redness and possible blistering of contacted skin within a day ( Fig 65.8 ) After to weeks, these skin findings evolve into hyperpigmentation, which may take several weeks or months to fade The skin is often painful rather than itchy Phytophotodermatitis often has a bizarre or geometric pattern, for example, linear streaks from dripping lime juice ( Fig 65.9 ) “Strimmer dermatitis” refers to a pattern of red, irregularly shaped macules and papules that can occur when power tools are used to cut plants, leading to buckshot spraying of plant material onto the skin Phytophotodermatitis may also be mistaken for child abuse Parents who touch furocoumarins can transfer them to their children via direct touch; children can then develop fingerprint-shaped hyperpigmentation in sun-exposed areas where the parent’s hand touched However, the individual lesions of phytophotodermatitis are usually uniform in color, in contrast to healing ecchymoses which usually have multiple hues within each lesion TABLE 65.4 COMMON PLANTS ASSOCIATED WITH PHYTOPHOTODERMATITIS Rutaceae family Lime (including key lime, Persian lime) Lemon Orange (including sweet orange, bitter orange, bergamot orange) Grapefruit Burning bush Apiaceae family Celery Parsnip Carrot Dill Parsley Meadow grass Common rue Hogweed Fennel Moraceae family Fig Other St John’s wort ...FIGURE 65.7 Polymorphous light eruption on the dorsal forearms and hands (From Gru AA, Wick M Pediatric Dermatopathology and Dermatology 1st ed Philadelphia, PA: Wolters Kluwer; 2018.) Juvenile