By Gary M. White, MD
Reticulated urticarial lesions on the dorsal hand 1 day after sun exposure.
Polymorphous light eruption or PMLE is an idiopathic reaction of the skin to ultraviolet light. The key clinical differential is lupus erythematosus. In a long-term followup study (23 years after an initial study) of 94 patients [AD 1998;134;1081], approximately a quarter no longer had symptoms and about half had milder symptoms. There seemed to be a correlation with autoimmune disease in women, but few patients went on to develop lupus.
Several hours to days after sun exposure, patients may develop papulovesicular, erythematous, lacy, urticarial, papular or plaque-type lesions. The face and neck are not typically affected as these areas, through regular exposure, harden to the sun's effects. Outbreaks occur in the summer and may affect any photoexposed area. Patients who travel to sun-intense areas for brief vacations may be most severely affected. ANA, SS-A, and SS-B should be obtained to exclude lupus erythematosus. Variants include juvenile spring eruption of the ears and springtime and summer eruption of the elbows.
Prevention of the disease by sun and visible light protection is the best approach. A sunscreen applied immediately upon wakening and reapplied several times a day is recommended. Because visible light may aggravate PMLE, physical block sunscreens (containing iron oxide, titanium dioxide and/or zinc oxide) should be used. For any active disease, a potent topical steroid is usually adequate although systemic steroids may be needed. Antimalarials (e.g., hydroxychloroquine 400 mg/d begun several days before and continued throughout the entire vacation) have been used as a preventative measure, as have gradually increasing doses of narrowband UVB.
NB-UVB may be started 3-4 weeks before vacation, 2-3 per week per protocol, as with psoriasis.
Polypodium leucotomos is a fern extract supplement for which there is some evidence of benefit in PMLE. Additionally, there is relatively good evidence from multiple studies of benefit for sunburn. The risk of sunburn is decreased and the MED (minimal erythema dose) is increased. The usual dose is 240 mg BID. See also sunburn.
Spring eruption of elbows is felt to be a variant of polymorphous light eruption. JAAD February 2013;Volume 68, Issue 2, Pages 306–312
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