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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 1 to
2 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 2 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 1 to
2 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 1 to 2 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