Polymorphous light eruption (PMLE) is a common seasonal disease that occurs in sun-sensitive people as a result of excessive exposure to sun. It is more common in young women at temperate latitudes and may totally ruin the summer holidays. The exact cause of polymorphic light eruption is unknown, but it is thought that delayed-type hypersensitivity immune reaction to ultraviolet radiation (UVR) plays an important role.
Polymorphic Light Eruption (PMLE) tends to run commonly on families (genetic) than general population. Individuals with family history of PMLE are more susceptible to this eruption. However, disease expression in genetically susceptible individuals is more dependent on environmental factors.
Signs and Symptoms of Polymorphous Light Eruption
Polymorphic light eruption manifests as itchy, red or skin-colored, non-scarring papules, vesicles, plaque and nodules that erupts symmetrically on sun exposed areas within few hours of sun exposure. In black individuals pinpoint papules are most common presentation. Some people might have skin tenderness on the affected areas. Some patients may also present with headache, fever and nausea. The rash usually worsens in spring and early summer and improves as the summer season progresses; this is known as “hardening.” The rash usually resolves fully without scarring over several days or week after avoiding the sun exposure.
The rashes are commonly seen on the V-area and back of the neck, dorsum of the hands and arms, malar area of the cheeks, bridge of nose and tip of the chin and less commonly on front and back of the legs.
Other conditions that may mimic like PMLE are:
- Solar Urticaria
- Acne, seborrheic or atopic eczema excerbated by sun exposure
- Xeroderma pigmentosum
- Erythropoietic protoporphyria
Pictures of PMLE
Complications are rare, but very few patients may develop lupus.
Treatment of Polymorphic Light Eruption
Mild cases of PMLE can be managed by avoiding UVR exposure and application of broad-spectrum sunscreen with at-least SPF 30. The area may be covered with clothing to further prevent PMLE.
In individuals with more severity and those prone to frequent eruption may be given a prophylactic photochemotherapy PUVA (psoralen plus UVA) or narrowband UVB phototherapy for prevention. Narrow band UVB is more favourable than PUVA as it has much fewer side effects than PUVA.  The course of treatment may be necessary on regular follow-up for few years. For patients with infrequent eruption, a short course of oral steroids may be given.
Other treatment options with mixed results include, antimalarials, nicotinamide, beta-carotene and omega-3 polyunsaturated fatty acids. Polypodium leucotomos extract have also been reported to be helpful in some patients but its efficacy have not been tested in large trial. [2,3]
Prevention of Polymorphic Light Eruption
One may prevent PMLE by avoiding excessive sun exposure, and regular use of broad-spectrum sunscreen (especially that protect against UVA radiation) . Wearing protective clothes may also help. Prophylactic phototherapy before going for vacation may also help prevent eruption.
- I.Man,R.S.Dawe,J.Ferguson. Artificial hardening for polymorphic light eruption: Practical points from ten years experience. Photodermatol Photoimmunol Photomed,15(1999),pp.96–99.
- H.Honigsmann.Polymorphous light eruption.Photodermatol Photoimmunol Photomed, 24 (2008), pp. 155–161.
- Tanew A,Radakovic S,Gonzalez S,Venturini M,et al.Oral administration of a hydrophilic extract of Polypodium leucotomos for the prevention of polymorphic light eruption.J Am Acad Dermatol. 2012 Jan;66(1):58-62.