eMedicine Specialties > Dermatology > Photo-Related Diseases
Polymorphous Light Eruption
Updated: Oct 23, 2009
Introduction
Background
Polymorphous light eruption (PMLE) is an acquired disease and is the most common of the idiopathic photodermatoses. PMLE is characterized by recurrent, abnormal, delayed reactions to sunlight, ranging from erythematous papules, papulovesicles, and plaques to erythema multiforme–like lesions on sunlight-exposed surfaces. Within any 1 patient, only 1 clinical form is consistently manifested.
Richards et al found that PMLE engenders a substantial psychosocial impact on patients who have the condition.1 Based on results from the Illness Perception Questionnaire sent to 302 patients and returned by 150 patients, 40% experienced emotional distress linked to PMLE. The psychological impact was related to the predicted consequences of PMLE, whereas health-related variables played a lesser role. Women associated more severe consequences linked to PMLE and were more emotionally distressed than men.
The face of a patient with polymorphous light eruption. Note the erythema and an indurated plaque.
Close-up view of polymorphous light eruption plaque.
Pathophysiology
The etiology of polymorphous light eruption (PMLE) is not fully known, and it is likely to be multifactorial. The immunologic pathogenesis of PMLE is supported by the study of timed biopsy samples of PMLE lesions. The CD4 subtype of T cells seen very early after exposure is replaced by CD8 lymphocytes 72 hours after irradiation. In general, findings conform to type IV delayed-type hypersensitivity mechanism.
In some PMLE lesions induced by UV-A, keratinocytes were found to express intercellular adhesion molecule 1 (ICAM-1).2,3 ICAM-1 is absent from normal keratinocytes, but it is known to be strongly induced by interferon gamma. The induction of ICAM-1 on keratinocytes results either from direct effects of UV on the promoter region of the ICAM-1 gene or from indirect effects of interferon gamma produced by activated lymphocytes aggregating in an underlying PMLE.
Intravascular and focal perivascular deposits of fibrin were detected in biopsy samples of PMLE papules. Vascular deposits of C3 and immunoglobulin M (IgM) were noted in a few patients. These findings may suggest that vascular injury with activation of a clotting cascade may play a role in the pathogenesis of PMLE. Repair of ultraviolet-damaged DNA is normal.
The demonstration that the female hormone 17beta-estradiol prevents UV radiation–induced suppression of the contact hypersensitivity response caused by the release of immunosuppressive cytokines (interleukin [IL]–10) from keratinocytes might thus explain why the risk of PMLE is higher in females than in males and why the risk decreases in women after menopause.4
Neutrophils may play a role in the development of PMLE. Immunohistochemical analysis by Schornagel et al in 2004 showed a significant decreased neutrophil infiltration in PMLE skin after UV-B irradiation compared with healthy case control subjects (P <.05).5 ICAM-1 and E-selectin expression on endothelial cells increased in both healthy controls and in the PMLE patients after UV-B irradiation. Chemotactic response towards IL-8 and C5a was not different between PMLE patients and healthy controls. The authors concluded that PMLE is marked by an altered immune response resulting in decreased skin infiltration of neutrophils after UV-B irradiation.
Kölgen et al noted that the reduced expression of tumor necrosis factor-alpha, IL-4, and IL-10 in the UV-B–irradiated skin of patients with PMLE.6 The reduction of these cytokines seems linked to a relative neutropenia and is a manifestation of decreased Langerhans cell migration and reduced TH2 skewing. An impairment of these mechanisms underlying UV-B–induced immunosuppression may be important in the pathogenesis of PMLE.7
Frequency
United States
Polymorphous light eruption (PMLE) affects about 10% of the US population. This figure is likely to be an underestimate because many patients do not seek medical attention. Many of the photodermatoses were lumped together before their individual pathogeneses were identified. PMLE is now a distinct clinical entity, as are many of the other photodermatoses (eg, solar urticaria, photoallergic dermatitis, hydroa vacciniforme, chronic actinic dermatitis, erythropoietic porphyria, lupus erythematosus).
Reported in 2007, Kerr and Lim identified 280 patients with photodermatoses.8 One hundred thirty-five (48%) were African Americans, 110 (40%) were white, and 35 (12%) were patients of other races. They noted a statistically significantly higher proportion of African Americans with PMLE compared with whites.
Benanni et al noted a low incidence of PMLE in renal transplant recipients,9 and Hönigsmann reports a prevalence of 10-20% in the United States and Western Europe.10
International
Deng et al used a questionnaire to survey 4899 residents (49% men and 51% women) of random Chinese villages in Yuan Jiang county (Dai and Hani minorities), Kunming city (Han people and Yi minority), Lijiang county (Naxi minority), and Shangri-La county (Zang minority).11 The altitudes of these regions were 380 meters, 1870 meters, 2410 meters, and 3280 meters, respectively. The prevalence of PMLE was 32 (0.65%) in 4899 residents and was 3.8 times higher in women compared with men. At higher elevations, the prevalence of PMLE increased. The mean time of sun exposure for PMLE was 6 h/d. The mean duration of PMLE was 5.8 years.
PMLE affects 21% of the population in Sweden.
Mortality/Morbidity
Expression of polymorphous light eruption (PMLE) may range from an insignificant, mild rash to severe disease affecting the patient's quality of life. Each case should be evaluated individually.
Richards et al found that emotional distress attributable to PMLE occurred in greater than 40% of individuals.1 Women more than men associated more severe consequences with their PMLE and experienced more emotional distress.
Race
Polymorphous light eruption (PMLE) affects all racial skin types, but it is more common in fair-skinned individuals with skin types I-IV than in other individuals. Overall, family history is positive for PMLE in about 15% of the patients. However, Native Americans have a hereditary form of PMLE with apparent autosomal dominant inheritance; 75% reveal disease in a family member.12
Sex
Polymorphous light eruption (PMLE) affects females 2-3 times more often than males. However, these data may be skewed because women are more likely to seek medical attention for cosmetic problems than males.
Age
Polymorphous light eruption (PMLE) usually has an onset in the first 3 decades of life. Men seem to have later onset of the disease than women.
Naleway et al reviewed records of 124 patients diagnosed with PMLE and found most were women and that the mean age of PMLE onset was 37.8 years.13 They noted only 4 required phototherapy treatment.
Clinical
History
Polymorphous light eruption (PMLE) tends to manifest in the spring.14 In addition, PMLE is a recurrent condition and patients state they have had the eruption before and that it went away as time passed.
- Sunlight is clearly the primary etiologic factor for PMLE.
- The eruption of PMLE typically occurs in spring or, rarely, in winter following ultraviolet radiation exposure reflected from snow.
- Typically, the lesions of PMLE first erupt at the onset of a vacation in a sunny place or at a high altitude and disappear by the time the patient returns home.
- The eruption decreases in severity as the summer progresses.
- The onset of the disease is sudden. The accompanying rash is pruritic and, in some instances, painful.
- Thirty minutes to several hours of exposure are required to trigger the eruption.
- Sun-exposed skin, especially that normally covered in winter (eg, upper chest, arms), is primarily affected, but autosensitization may lead to a generalized involvement.
- The rash appears within hours to days of exposure, and it subsides over the next 1-7 days without scarring.
- Most patients have associated pruritus, but some patients describe stinging and pain.
- Occasionally, patients experience systemic flulike symptoms after sun exposure.
- Unless severe and particularly bothersome, many patients do not visit a physician for PMLE rash. It is often discovered incidentally.
- Jansén traced the natural history of chronic PMLE in 138 people, 85 of whom were female.15 Their mean age was 26.4 years. The length of time in the study was 10.5 years. In 57% of cases, the PMLE happened in a rapid fashion. It started in a small photoexposed area in 88% of cases, and extended to a greater area each year. Light sensitivity tended to increase with each subsequent year. The patients’ threshold tolerance to solar radiation occurred 30 minutes after exposure in £60% of patients. In 50% of patients, yearly hardening phenomena occurred. Ocular and oral involvement occurred in 46% and 49% of the patients, respectively. About 66% patients experienced some general symptoms after solar radiation exposure.
Physical
As the name implies, clinical manifestations of polymorphous light eruption (PMLE) vary. Many different morphologies may appear on sun-exposed areas, but, usually only one morphology dominates in a given individual.
- Papules (greatest incidence), plaques, papulovesicles, and erythema multiforme–like lesions are the most common morphologies. Photosensitive erythema multiforme and erythema multiforme–like PMLE can be difficult to distinguish clinically. Combined morphological types of lesions, while uncommon, do occur. For example, the small papular variety may coalesce to form an eczematous type and large papular lesions may produce plaques or assume an annular configuration.
Papular variant of polymorphous light eruption.
Large facial plaques.
- Sun-exposed skin, especially that normally covered in winter (eg, upper chest, arms), is affected primarily, but autosensitization may lead to a generalized involvement.
- Cheilitis is uncommon in patients in the United States. In such patients, the rare diagnosis of actinic prurigo is a more likely cause of the inflammatory photosensitivity disorder. Cheilitis often occurs in the tropics and, when this is the case, can be the only manifestation of the PMLE. That is, it can manifest without involvement of the extremities, face, or torso. In the case of photosensitive cheilitis, PMLE must be distinguished from chronic actinic cheilitis and the eczematous cheilitis produced by photosensitizing agents.
- In African Americans, a variant of PMLE with pinpoint papules (1-2 mm) can be observed on sun-exposed areas, sparing the face and flexural surfaces.16
Causes
Although most authorities now consider UV-A light as the causative factor in polymorphous light eruption (PMLE) eruption, UV-B, or even visible light, may be responsible in some individuals
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References
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Further Reading
Keywords
polymorphous light eruption, polymorphic light eruption, PLE, PMLE rash, idiopathic photodermatosis, reaction to sunlight, ultraviolet radiation exposure, UV-R exposure, erythema multiforme–like lesions
