Polymorphic light eruption

Polymorphic light eruption is an idiopathic photosensitivity disorder. Within hours of sun exposure, pruritic erythematous papules, plaques or vesicular lesions appear on exposed skin of the forearms and upper chest. The condition usually occurs in spring rather than in winter, when background sun exposure is higher and fewer body areas are covered with clothing. The lesions fade over several days without scarring. See here for photos of polymorphic light eruption.

Differential diagnoses include solar urticaria (physical urticaria caused by exposure to sun), cutaneous lupus erythematosus, and photosensitive drug eruption (see Types of cutaneous drug reactions, their time courses, and some commonly implicated drugs). Seek dermatologist advice for confirmation of diagnosis.

Advise patients to use broad-spectrum sun protection. Ultraviolet A (UVA) is the most common precipitating wavelength.

For symptomatic relief of the rash (particularly if it is vesicular) use:

1betamethasone dipropionate 0.05% ointment topically, twice daily betamethasone dipropionate betamethasone dipropionate betamethasone dipropionate

OR

1mometasone furoate 0.1% ointment topically, twice daily. mometasone furoate mometasone furoate mometasone furoate

For severe episodes of polymorphic light eruption, a short course of oral corticosteroids can be used. Use:

prednisolone (or prednisone) 25 mg orally, once daily for 3 to 5 days. prednisolone prednisolone prednisolone

If these measures are ineffective, refer to a dermatologist. Phototherapy may be used to improve the skin’s tolerance of UV light. Alternative therapies include hydroxychloroquine and ciclosporin.

Figure 1. Polymorphic light eruption

Note:

Photo sourced with permission from Dr Jonathan Chan.

Note:

Photo sourced with permission from Dr Jonathan Chan.

Note:

Photo sourced with permission from Dr Jonathan Chan.