What is Polymorphous Light Eruption?

Patient Presentation
A 17-year-old female came to clinic because of a pruritic skin rash for 3 days.
She was on a spring break vacation to a beach and noticed the rash on her arms and top of her legs.
She said she felt her skin become ‘tingly’ towards the end of one afternoon that increased in intensity. She noticed that her skin looked liked a sunburn in that it was ‘bumpy’ and seemed to itch more than be painful.
She used some moisturizing lotion on the rash but she said that didn’t seem to make a difference. Over the evening she said that the intensity of the itchiness gradually faded.
In the morning of the second day, the bumpiness was still there and it would itch if she accidentally bumped the areas. When she went outside the itchiness increased almost immediately. She put on long-sleeved shirt and a long pair of shorts that covered the rashes which seemed to help some.
She had been using the same sunscreen during this vacation that she had used previously. She denies any new soaps, lotions, deodorants, clothing, detergents, etc.
The past medical history was non-contributory.
The review of systems was negative including fever, joint complaints, difficulty breathing or swallowing.
The pertinent physical exam showed a well-appearing female with mild sunburn to her face, back of neck and ears. On the extensor surfaces of her forearms, upper arms and top-front of her legs bilaterally, she has an intensely red, blanching rash that has fine confluent papules, some of which look like they may be vesicular.
Palpation causes her to have a mildly painful pruritus.
The diagnosis of polymorphous light eruption was made. The patient was instructed to avoid the sun as much as possible and to use protective clothing and sunscreen. For her comfort she was told that she could use diphenhydramine. She was also told that this could improve within a few days to two weeks but could recur.

Discussion
Photodermatosis is any dermatosis caused by exposure to light. These photodermatoses can be normal responses to excessive sunlight or could be a photosensitivity. Photosensitivity is a general term describing an abnormal reactivity to sunlight by the skin.
Idiopathic photosensitivity reactions include:

• Actinic Prurigo – is also called hydroa aestivale and Hutchinson’s summer prurigo. It is commonly seen in Indians and mixed ancestry people of Mexico, Central American and South America. Intensely pruritic papules, plaques and nodes occur with excoriations and scars. It generally affects exposed areas but can also be seen in covered areas particularly the lower back and buttocks. It can be seen year round but is worse in the spring and summer with improvement in the fall.
• Juvenile spring eruption – is a photosensitivity where there are edematous, red papules mainly on the helix of the ears that can become vesicular and crusted. Dorsum of the hands and the trunk can also be involved. It is third more common in boys than girls and usually resolves within 1 week.
• Polymorphous light eruption – see below
• Solar urticaria – is a Type 1 IgE-mediated hypersensitivity reaction that causes localized urticarial flare reaction during or within 30 minute of light exposure. The skin returns to normal after a few hours and will not recur within 12-24 hours even with more sunlight exposure. It occurs often in females in the 3rd to 4th decade but can be seen as early as age 2 years.

Learning Point
Polymorphous light eruption is the most common idiopathic photosensitivity reaction. It is sometimes referred to as “sun poisoning” or “sun allergy”. It is most often found in females in the second or third decade of life and occurs in 10-15% of the U.S. population.
An autosomal-dominant form has been described in North and South American natives. It appears to be an immune-mediated, delayed type hypersensitivity reaction to UV rays in the 290-480 nm range papules but its exact etiology is unknown.

The skin is described a having pleo- or poly-morphic lesions that range from small papular, urticarial, vesicular or eczematous lesions to large papules and plaques that can look like erythema multiforme. The lesions generally occur 1-2 days after intense sunlight.
They are located on sun exposed areas such as the face, arms, hands and sides of the neck. The pruritus can be quite severe and the lesions resolve within 1-2 weeks if no additional sunlight exposure occurs. For some people the lesions can occur in the spring and persist, but improve as the skin gets used to the sun exposure over the summer.

The diagnosis is made clinically, but phototesting can be done. With phototesting, the expected reaction occurs in hours, lasts days and is not urticarial. Sometime systemic lupus erythematosus may present with similar lesions and serological testing is necessary.

Images of polymorphic light eruption can be found in the eMedicine and Google Image references below in To Learn More.

Questions for Further Discussion
1. What medications commonly cause photosensitivity?
2. What is phytophotodermatitis?

Related Cases

Disease
Polymorphous Light Eruption
Sun Exposure
Skin Conditions

Symptom/Presentation
Rash
Urticaria and Pruritis

Specialty
Dermatology

Age
Teenager

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MedlinePlus for this topic: Sun Exposure

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Scheinfeld NS, Shirin S, DelRosario R, Winkielman A. MDPolymorphous Light Eruption. eMedicine.
Available from the Internet at http://www.emedicine.com/derm/topic342.htm (rev. 3/9/06, cited 4/9/07).

Paller AS, Mancini AJ. Hurwitz Clinical Pediatric Dermatology. Elsevier Inc. 2006;505-507.

ACGME Competencies Highlighted by Case