Polymorphous Light Eruption

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Practice Essentials

Polymorphous (polymorphic) light eruption (PMLE) is an acquired disease and is the most common of the idiopathic photodermatoses. First described by Ebstein in 1942 as prurigo aestivalis, 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. (See Presentation.) The word polymorphous in the name refers to the different morphologic presentations that the condition can have. In any single patient, however, only one clinical form is consistently manifested.

PMLE can have a substantial psychosocial impact. In a review by Richards et al, as many as 40% of patients described emotional distress related to PMLE.[1]  Women associated more severe consequences with PMLE and were more emotionally distressed than men. Patients experience a decrease in quality of life as a consequence of their efforts to avoid sun exposure.

Management of PMLE includes strict sun protection. This can be accomplished by using broad-spectrum sunscreens, seeking shade, and wearing protective clothing, including hats. Photohardening is beneficial and can be initiated early in spring to enhance tolerance of sun exposure. Topical and systemic immunosuppressants are employed for symptom management. The use of these agents should be tailored to the individual patient, with benefits weighed against risks. (See Treatment.)

Benign summer light eruption (BSLE) has been proposed as a possible subset of PMLE that might be milder and more driven by ultraviolet (UV) A (UVA) light.[2]

Pathophysiology

The production of neoantigens, failure to induce apoptosis, poor immune tolerance, delayed hypersensitivity reaction, and skin microbiome dysregulation are important factors in the pathogenesis of PMLE. The action spectrum is primarily UVA light but can include UVB light. Some patients even react in the visible light spectrum. It has also been shown that UVC can cause PMLE.[3]

Actinic prurigo (AP) is thought to be a subtype of PMLE, given that they have a common pathophysiology. AP tends to persist longer, and lesions can involve the mucosa, including the conjunctiva. Excoriations and scaring are other features of AP not seen in PMLE. Human leukocyte antigen (HLA)-DR4 is strongly associated with AP.[4]

Delayed hypersensitivity reaction 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.[5, 6]

Kölgen et al noted that the reduced expression of tumor necrosis factor (TNF)-α, interleukin (IL)-4, and IL-10 in the UVB-irradiated skin of patients with PMLE. The reduction of these cytokines seems linked to a relative neutropenia and is a manifestation of decreased Langerhans cell migration and reduced TH2 skewing.[7] An impairment of these mechanisms underlying UVB-induced immunosuppression may be important in the pathogenesis of PMLE.

An increase in the IL-1 family of cytokines (in particular, IL-36 gamma) in skin lesions and peripheral blood of PMLE patients indicates an enhanced focal and systemic immune response. This further supports the enhanced immune response upon UV exposure.[8]

In a study (N = 48) by Koulu et al comparing patients with PMLE (n = 24) with 24 healthy sex-matched and age-matched control subjects (n = 24), the two groups had similar degrees of immunosuppression of contact sensitization to diphenylcyclopropenone due to earlier exposure to solar-simulating UV radiation.[9] However, of the patients with PMLE who were immunosuppressed by UV radiation, only one exhibited immunotolerance to the same allergen 10-24 months later. The study concluded that impaired propensity to UV-induced, allergen-specific immunotolerance may promote recurrent PMLE.

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 the skin of PMLE patients after UVB irradiation compared with healthy control subjects.[10] Intercellular adhesion molecule 1 (ICAM-1) and E-selectin expression on endothelial cells increased in both healthy controls and in PMLE patients after UVB irradiation. Chemotactic response towards IL-8 and C5a was not different between the two patient groups. The authors concluded that PMLE is marked by an altered immune response resulting in decreased skin infiltration of neutrophils after UVB irradiation.

Apoptotic keratinocytes produce photoneoantigens, and failure to clear these antigens leads to an increased immune response. In photoprovocated skin samples of PMLE patients, gene expression of apoptotic cell clearance C1S and SCARB1 are reduced.[11] This, along with the failure in immune tolerance, leads to PMLE skin lesions with light exposure. In fact, this might explain the reduced rate of skin cancer in patients with PMLE.[12, 13]

Regarding microbiome dysregulation, UV-induced changes to the skin microbiome in PMLE patients was proposed as an initiating or provoking factor in the inflammatory cascade, via antimicrobial peptide (AMP) release and activation of the innate immune system. A unique pattern of AMP was seen in PMLE patients as compared with patients with atopic dermatitis, psoriasis, or normal skin. Increases in psoriasin, RNAse7, human beta defensin-2 (HBD‐2), and LL37 are seen in PMLE, similar to those seen in psoriasis. However, PMLE patients had a lower level of HBD-3 than patients with psoriasis or atopic dermatitis.[8, 14]

In a study by Muhlbauer et al, intravascular and focal perivascular deposits of fibrin were detected in biopsy samples of PMLE papules.[15] 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.

In some PMLE lesions induced by UVA, keratinocytes were found to express ICAM-1.[16, 17] 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 (IFN) gamma produced by activated lymphocytes aggregating in an underlying PMLE.

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 (IL-10) from keratinocytes might explain why the risk of PMLE is higher in females than in males and why the risk decreases in women after menopause.[18]

It has been suggested that glutathione S-transferases (GSTs) act to protect against PMLE; however, a study of the isoenzymes of the GST genes GSTM1, GSTT1, and GSTP1 found no protective relationship of these isoenzymes to PMLE.[19]

It is possible that the use of tobacco makes PMLE worse.[20]

Etiology

The etiology of PMLE is not fully known but is likely to be multifactorial. That PMLE clusters in families suggests a genetic component. Millard et al studied 420 pairs of adult twins and found that 21% of monozygotic twins and 18% of dizygotic twins had PMLE.[21]  A first-degree family history was seen in 12% of affected twins, compared with 4% of unaffected twins. The prevalence of PMLE in first-degree family members has been reported as 20.9%.[22]

The UVA light spectrum is the most common causative factor in polymorphous light eruption (PMLE). Other wavelengths, including UVB or even visible light, may also induce PMLE in some individuals. PMLE-like lesions have been reported in welders, resulting from exposure to UVC light.[23]

Overall, family history is positive for PMLE in about 15-20% of patients. However, Native Americans have a hereditary form of PMLE with apparent autosomal dominant inheritance; 75% reveal disease in a family member.[24]

Epidemiology

United States and international statistics

PMLE affects about 10-20% of the population in the United States and Western Europe.[25]  Given that many patients do not seek medical attention, this figure is likely to be an underestimate. In addition, many of the photodermatoses were previously lumped together before their individual pathogeneses were identified. PMLE is currently regarded a distinct clinical entity, as are many of the other photodermatoses (eg, solar urticaria, photoallergic dermatitis, hydroa vacciniforme, chronic actinic dermatitis, erythropoietic porphyria, and lupus erythematosus).

Benanni et al noted a low incidence of PMLE in renal transplant recipients; this can be attributed to the immunosuppressants used to prevent rejection.[26]

Deng et al (N = 4899; 49% men, 51% women) used a questionnaire to survey residents of randomly selected villages in several Chinese counties that lay at different altitudes and haddifferent ethnic majorities.[27] The overall prevalence of PMLE was 0.65% (32/4899) residents and was 3.8 times higher in women than in men. At higher elevations, the prevalence of PMLE increased. The mean time of sun exposure for PMLE was 6 hours per day. The mean duration of PMLE was 5.8 years.

A report from India in 2013 noted that PMLE was the most common photodermatitis after chronic actinic dermatitis, whereas hydroa vacciniforme and solar urticaria were uncommon.[28] Furthermore, the report stated that lichenoid PMLE and pinpoint papular PMLE were the most common types found in the subcontinent.

A systematic review of population-based studies in the English literature found that the prevalence of PMLE ranged from a low of 0.65% (in China) to a high or 21.4% (in Ireland).[29]

Age-related demographics

PMLE usually has its onset in the first three decades of life, though onset may also occur during childhood and late adulthood. The onset of the disease seems to be later in men than in women.

Studies have reported mean ages of 26.4 years and 37.8 years in their respective cohorts.[30, 31]

Sex-related demographics

PMLE has been reported to affect females two to three times more often than males; however, these figures may be skewed because females are more likely to seek medical attention than males.

Race-related demographics

PMLE affects all racial skin types. In a Scandinavian/Mediterranean study, PMLE was more common in patients with Fitzpatrick skin type I. The papular variant can involve the face and seems most common in patients with Fitzpatrick skin types III-VI.[32, 33]

PMLE has been reported to be significantly more common in light-skinned individuals than in dark-skinned individuals.[34] In a study of 280 American patients with photodermatoses,[35]  135 (48%) were African Americans, 110 (40%) were Whites, and 35 (12%) were patients of other races.[35]  The percentage of patients with PMLE was found to be significantly higher in African Americans than in Whites. One study of a cohort of 229 patients with photodermatoses reported that 63 (42.2%) were White and 138 (46.6%) were African American and that PMLE was present in 54% and 86.2% of the patients, respectively.[36]

Prognosis

Expression of PMLE may range from an insignificant, mild rash to severe disease affecting the patient's quality of life. Some PMLE patients experience a less severe reaction with each consecutive year, but many patients have reactions that may worsen with time without appropriate treatment. Each case should be evaluated individually.

PMLE is a chronic condition; the average time to resolution is long and may extend to 30 years. A registry analysis (N = 97) by Gruber-Wackernagel et al determined that 74% of PMLE patients were still experiencing symptoms after 20 years.[37]

Richards et al found that emotional distress attributable to PMLE occurred in more than 40% of individuals.[1] Women were more likely than men to associate more severe consequences with their PMLE and to experience more emotional distress.

History

Polymorphous (polymorphic) light eruption (PMLE) tends to manifest in the spring and early summer; it may also manifest in the winter involving the face as a result of sunlight reflected off snow.[38] In addition, PMLE is a recurrent condition, and patients typically state that they have had the eruption before and that it went away as time passed.

In most cases, the lesions of PMLE first erupt after exposure to strong sun following a period of relative photoprotection—for example, at the onset of a vacation in a sunny place or at a high altitude in early spring. 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. Triggering of the eruption takes 30 minutes to several hours of sun exposure. The rash appears within hours to days of exposure, and it usually subsides over the next 1-7 days without scarring, though in some cases it has been reported to persist for as long as 5 weeks.[39] Sun-exposed skin, especially skin in areas normally covered in winter (eg, upper chest and arms), is primarily affected, but autosensitization may lead to a generalized involvement. Most patients have associated pruritus; some describe stinging and pain.

Occasionally, patients experience systemic flulike symptoms after sun exposure.

Many patients do not visit a physician for a PMLE rash unless the rash is severe and particularly bothersome.

A study (N = 138; 85 females, 53 males) by Jansén traced the natural history of chronic PMLE for 10.5 years.[31]  In 57% of cases, PMLE developed rapidly. Lesions often began in a small photoexposed area and extended to a larger area each year. Light sensitivity tended to increase with each subsequent year. In 50% of patients, yearly hardening phenomena occurred. Ocular and oral involvement were noted in 46% and 49% of patients, respectively. About 66% patients experienced some general symptoms after solar radiation exposure.

Physical Examination

As the name implies, clinical manifestations of PMLE vary. Many different morphologies may appear on sun-exposed areas, but usually, only one morphology dominates in a given individual.

Papules (the most common manifestation), plaques, papulovesicles, and eczematous and erythema multiforme–like lesions are the morphologies most frequently seen. Photosensitive erythema multiforme and erythema multiforme–like PMLE can be difficult to distinguish clinically. Combined morphologic types, though 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. (See the images below.)



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Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/Watermar....



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Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/Watermar....



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Polymorphous light eruption on the arm. Courtesy of Waikato District Health Board and DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_re....



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Polymorphous light eruption on the thighs and hand. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/reactions/pmle2.jpg).

As noted, it is primarily sun-exposed skin that is involved, but a generalized involvement may develop as a result of autosensitization.

Cheilitis is uncommon in the United States. In this setting, the rare diagnosis of actinic prurigo (AP) is a more likely cause of the inflammatory photosensitivity disorder. Cheilitis is more common in the tropics, where it might be the only manifestation of PMLE. In the case of photosensitive cheilitis, PMLE must be distinguished both from chronic actinic cheilitis and from the eczematous cheilitis produced by photosensitizing agents.

Other variants of PMLE include a pinpoint papular variant observed in African Americans, benign summer light eruption (BSLE),[2] solar purpura, juvenile spring eruption (JSE), localized PMLE, scar PMLE, and PMLE sine eruptione.

The pinpoint variant seems to be observed in patients with Fitzpatrick skin types IV-VI.[33] African Americans present with pinpoint papules (1-2 mm) that can be observed on sun-exposed areas, sparing the face and flexural surfaces.[40] This variant has also been described in a series from Singapore[41] and in a series of 34 Taiwanese patients whose rash resolved with sun protection.[32] Ten of these Taiwanese patients had mild spongiosis on biopsy.

BSLE presents in a mild form.

JSE presents in children, with papules or papulovesicles that can erode and typically involve the helices of the ears. JSE is more common in boys than in girls, likely because girls traditionally have longer hair that protects their ears from sunlight exposure.

In a retrospective study from Spain, Molina-Ruiz et al suggested that five men and four women had a localized variant of PMLE that they referred to as spring and summer eruption of the elbows.[42] The authors did not determine the mechanism by which the lesions were confined to these specific areas. A small case series (N = 5) by de Gálvez et al subsequently confirmed this variant through photoprovocation and histopathology.[43]

Scar PMLE that can occur on hypopigmented scars has been noted in India.[44]

PMLE sine eruptione presents with no visible lesions but with symptoms of pain or pruritus upon exposure to ultraviolet (UV) light.

Approach Considerations

The diagnosis of polymorphous (polymorphic) light eruption (PMLE) is usually based on the clinical picture and the history.

Laboratory Studies

Laboratory tests can be performed to rule out other dermatoses other than PMLE, such as erythropoietic protoporphyria or lupus erythematosus. Antinuclear antibody (ANA), anti-Ro (SS-A), and anti-La (SS-B) tests, as well as urine, stool, and blood porphyrin levels, should be obtained when clinically indicated.[47]

Normal titers of ANA, as well as normal urine, stool, and blood porphyrin levels, support the diagnosis. A false-positive ANA can be seen; a titer of 1:80 has been reported in up to 13% of normal population.

Other Tests

Results of phototesting in PMLE patients have been controversial, ranging from ability to reproduce the eruption by repeat phototesting in 60-100% of patients to inability to reproduce it except in patients who are highly photosensitive.[48] These differences may be explained by lack of standardized test procedures, variation in radiation sources used, and imprecision in diagnostic criteria for the disease. Minimal erythema doses (MEDs) are normal in PMLE and lowered or abnormal in chronic actinic dermatitis. In solar urticaria, irradiation results in reproduction of the lesion.

Photoprovocation test

This test involves repetitive light testing in which the right forearm is irradiated with three times the MED to UVA and the left forearm with three times the MED to UVB for 3 consecutive days. Results are read immediately and then at 24 and 72 hours. A delayed reading at 1 week may also be helpful. Test results are often positive in PMLE; however, a negative result does not exclude the diagnosis.

If a lesion (eg, a papule or vesicle) develops, biopsy can be performed for confirmation. Histologically, a superficial and deep perivascular lymphocytic infiltrate is apparent with dermal edema. The test is best done in spring or early summer to avoid false-negative results. The area for testing should include a skin site previously involved with PMLE.

Photopatch tests

These can be used to rule out photoallergic or airborne contact. Two identical strips of standard photoallergens are placed on the back, and one of them is exposed to UVA radiation 24 hours later. Both the irradiated site and the unirradiated site are read at 24, 48, and 96 hours. the occurrence of a positive reaction at the irradiated site but not at the unirradiated site is diagnostic of a photocontact allergy. The occurrence of positive reactions at both sites is indicative of a contact allergy. A study by Leroy et al suggested that polychromatic phototesting seems to be more sensitive than UVA phototesting for assessing PMLE and that UVB is a key trigger of PMLE.[49]

Photopatch testing is useful for differentiating PMLE from other conditions that may cause photosensitivity, such as photoallergic contact dermatitis (PACD), allergic contact dermatitis (ACD), and chronic actinic dermatitis (CAD).[50]

Histologic Findings

The most striking feature of the biopsy specimen from a patient with PMLE is edema in the upper part of the dermis (see the first and second images below). Tight perivascular lymphocytic infiltrate is observed in the upper and middle dermis. When eczematous epidermal changes are present clinically, spongiosis, edema, dyskeratosis, and basal cell vacuolization may be observed. Occasionally, neutrophils and eosinophils may be present in the infiltrate; however, the dominant cell is the lymphocyte (see the third and fourth images below).



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Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathol....



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Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathol....



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Polymorphous light eruption pathology showing papillary dermal edema with lymphocytes in the epidermis (exocytosis). Courtesy of DermNet New Zealand (....



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Polymorphous light eruption pathology. The infiltrate is mainly lymphocytic but there may be intermixed eosinophils, neutrophils, and histiocytes. Cou....

Mucin, which is thought to distinguish PMLE from lupus, can be present in skin biopsy specimens from PMLE patients. A study of dermal mucin in lupus samples found that it was not greatly different from that in PMLE samples, whereas other dermatitides (eg, erythema multiforme, fixed drug eruption, graft versus host disease, lichen planus, photodamaged skin) also had some mucin but significantly less of it.[51]  

The erythema multiforme subtype can show evidence of a vacuolar interface with liquefactive degeneration of the dermoepidermal junction. A predominantly neutrophilic subtype also can be seen, which may be confused with Sweet syndrome. Chilblains has similar pathologic features, but the history and location of the lesions can usually help make the diagnosis.

Medical Care

Photoavoidance

Photoavoidance (eg, avoiding sunlight, wearing protective clothing, using sunscreen) remains a key factor in the care of patients with polymorphous (polymorphic) light eruption (PMLE). Broad-spectrum sunscreens are recommended because sunscreens with high sun protection factor (SPF) values are not necessarily protective against ultraviolet (UV) A (UVA)-induced PMLE.

DeLeo et al reported that sunscreen with four UVA filters (ie, ecamsule 3%, octocrylene 10%, avobenzone 2%, and titanium dioxide 5%) was more effective for preventing PMLE flares than a sunscreen with only a triad of UVA blockers.[52] Other studies have supported the use of UVA blockers to help prevent PMLE,[53] including a report that described a lower percentage of PMLE (0% at 2 mg/m2; 33% at 1 mg/m2) in subjects who used high UVA sunscreen protection than in those who used lower UVA sunscreen protection (73% at 2 mg/m2; 80% at 1 mg/m2).[54]

Phototherapy

Phototherapy with UVA1, narrowband UVB, psoralen plus UVA (PUVA), or broadband UVB can harden the skin against the development of PMLE. Aljasser et al reported a case of PMLE that failed UVA1 therapy, in which a woman aged 37 years developed a recalcitrant PMLE that lasted 5 weeks after completion of UVA1 phototherapy.[39] Treatment given at the beginning of spring for several weeks may prevent flare-ups throughout the summer.

Several studies found PUVA to be superior to UVB, controlling the outbreaks in 90% of patients.[55] In a study of 25 patients with severe PMLE, narrowband UVB (311 nm) was found to be an equally effective alternative to PUVA.[56] Oral prednisone may be useful in conjunction with phototherapy to avoid eruption during therapy. Barolet et al reported on the use of light-emitting diode nonthermal therapy as a prophylactic measure for PMLE.[56]

Antioxidants

Antioxidants have also been suggested for helping to prevent PMLE lesions. In a randomized, double-blinded, placebo-controlled clinical study by Hadshiew et al, the efficacy of a new topical formulation was compared with that of a broad-spectrum sunscreen.[57] The new product contained 0.25% alpha-glucosyl-rutin (a natural, modified flavonoid) and 1% tocopheryl acetate (vitamin E). Thirty patients with a history of PMLE were pretreated with the cream 30 minutes prior to daily photoprovocation with UVA irradiation of 60-100 J/cm2 to the upper arms.

A statistically significant difference was found between the antioxidant-containing formulations and both the placebo and the sunscreen-only formulation.[57] Only a single patient treated with the new antioxidant UV-protective gel formulation developed clinical signs of PMLE in the area treated. In comparison, 62.1% of the placebo-treated areas and 41.3% of the sunscreen-only treated areas showed mild-to-moderate signs of PMLE. The authors suggested that combining a potent antioxidant with a broad-spectrum sunscreen could be far more effective in preventing PMLE than sunscreen alone.

The use of topical antioxidants such as 0.25% alpha-glucosyl-rutin and 1% vitamin E along with a broad-spectrum highly UVA-protective sunscreen was found to be helpful in PMLE patients.[58]

Vitamins

Some authorities believe that vitamin therapy is helpful in the treatment of PMLE. In a study by Neumann et al, a regimen of nicotinamide 3 g/day PO for 2 weeks was successful in 60% of 42 patients.[59] The rationale for using nicotinamide was the knowledge that it blocks the formation of kynurenic acid, a photosensitizer that may play a role in PMLE. Ahmed et al found that oral vitamin E supplementation (400 IU) and use of sunblock decreased the markers of oxidative stress and lipid peroxidation in patients with PMLE.[58]

Systemic vitamin C and vitamin E have not been found to prevent photoprovocation test reactions in persons with PMLE.[60]

The preventive effect of topical calcipotriol (an analogue of calcitriol, 1,25-dihydroxyvitamin D3) was described in a randomized double-blinded placebo-controlled trial by Gruber-Wackernagle et al.[61]  Thirteen patients with PMLE applied cream (calcipotriol or placebo) topically to symmetrically located pairs of test areas twice daily for 7 days before photoprovocation with solar-simulated UV radiation was begun. A specific PMLE test score was used to rate symptom severity at 48, 72, and 144 hours after the first photoprovocation exposure. Pretreatment with calcipotriol, compared with placebo, significantly reduced PMLE symptoms by an average of 32%.

Corticosteroids

Topical corticosteroids are useful, as would be expected in many dermatoses associated with lymphocytic skin infiltrate. They are temporary measures for symptomatic relief. Adverse effects such as potential tachyphylaxis and skin atrophy limit their long-term use.

Systemic steroids may be needed to suppress acute flares or extensive generalized eruption. Adverse effects of prolonged systemic steroid use include decreased glucose tolerance, osteoporosis, impaired immunity, and weight gain. Obviously, this treatment can only be offered intermittently and for a short period. It may also be considered for prophylactic use in patients who are going on vacation or patients experiencing other unavoidable sun exposure.

Other agents

Antihistamines may help with pruritus.

Antimalarials at low doses are sometimes helpful, especially in patients with a large papular variety of PMLE. In a comparative study by Pareek et al, a good-to-excellent response was reported by 68.9% of the patients who received hydroxychloroquine and by 63% of the patients who received chloroquine.[62]

Beta carotene, which is effective in erythropoietic protoporphyria, may be an alternative to chloroquine. Oral carotenoid preparation (beta carotene and canthaxanthin in a daily total dose of 100 mg) was compared to hydroxychloroquine (200 mg/day).[63] Both offered full sun tolerance in an equal but small percentage of patients in comparison with a placebo.

Azathioprine was reported to be effective in two cases of recalcitrant severe disease at 0.8-2.5 mg/kg/day for 3 months.[64] In one patient, the effect lasted up to 4 months after therapy was discontinued. Given the limited available data, however, as well as the toxicity of azathioprine, extreme caution must be exercised when this form of treatment is chosen.

Other therapies (eg, cyclosporine) can be helpful, but further studies are needed to determine their benefits.[12]

Interest in the use of thalidomide for a number of dermatoses (eg, Behçet syndrome, cutaneous lupus, porphyria cutanea tarda, and PMLE) has been reemerging. The immunomodulatory action on subsets of T cells was proposed as a mechanism. Thalidomide (50-200 mg PO at bedtime) has reportedly been very effective for Native American patients with PMLE. The most commonly described adverse effects have been sedation, constipation, and weight gain. The most serious complications of thalidomide therapy are peripheral neuropathy and teratogenicity.

Polypodium leucotomos, a tropical fern extract, was found to be helpful in delaying PMLE symptoms.[65, 66] The dose ranged from 720 to 1200 mg/day, based on weight. It was protective in 30% and 28% of patients for UVA-induced and UVB-induced PMLE, respectively.

Afamelanotide may alleviate symptoms of PMLE by increasing the pigment in the skin, and it could be photoprotective for some patients.[67] Afamelanotide is injected subcutaneously at a dose of 20 mg, with slow release. This leads to increased melanization in sun-exposed skin.

Prevention

The importance of avoiding sunlight during the hours of most intense UV irradiation (from 10:00 AM to 2:00 PM) and wearing protective clothing (eg, hats, gloves, long pants, long sleeves) should be emphasized to PMLE patients. Blue denim clothing is particularly beneficial in terms of sun protection. Wide-spectrum sunscreens with a high SPF and UVA protection should be applied and reapplied during the day. The inclusion of both ecamsule and avobenzone in one sunscreen preparation has been shown to be clinically beneficial for PMLE patients as compared with sunscreen preparations containing either ecamsule or avobenzone alone; each agent filters UVA individually.[53]

Medication Summary

The goals of pharmacotherapy for polymorphous light eruption (PMLE) are to reduce morbidity and to prevent complications.

Hydroxychloroquine (Plaquenil)

Clinical Context:  Hydroxychloroquine inhibits chemotaxis of eosinophils, locomotion of neutrophils, and impairs complement-dependent antigen-antibody reactions.

Hydroxychloroquine sulfate 200 mg is equivalent to 155 mg hydroxychloroquine base and 250 mg chloroquine phosphate.

Class Summary

These agents may have immunomodulatory effects.

Prednisone (Deltasone, Meticorten, Orasone)

Clinical Context:  Prednisone is an immunosuppressant for the treatment of autoimmune disorders; it may decrease inflammation by reversing increased capillary permeability and suppressing polymorphonuclear activity. Prednisone stabilizes lysosomal membranes and suppresses lymphocyte and antibody production. 

Class Summary

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. In addition, these agents modify the body's immune response to diverse stimuli.

Thalidomide (Thalomid)

Clinical Context:  Thalidomide is only supplied to pharmacies participating in the System for Thalidomide Education and Prescribing Safety (STEPS) program. It is an immunomodulatory agent that may suppress excessive production of tumor necrosis factor-alpha and may down-regulate selected cell surface adhesion molecules involved in leukocyte migration.

Class Summary

These agents modify the activity of key factors in the immune system.

Beta carotene

Clinical Context:  Beta-carotene may provide a limited level of photoprotection. It causes yellowing of skin (carotenoderma). Any photoprotection afforded increases slowly after the drug is commenced over a 4- to 6-week period. When discontinued, skin color and benefit fade over several weeks.

Niacin (Vitamin B-3)

Clinical Context:  The source of niacin is used in tissue respiration, lipid metabolism, and glycogenolysis.

Class Summary

These agents are essential for normal DNA synthesis and cell function.

What is polymorphous light eruption (PMLE)?What is the pathophysiology of polymorphous light eruption (PMLE)?What causes polymorphous light eruption (PMLE)?What is the prevalence of polymorphous light eruption (PMLE) in the US?What is the global prevalence of polymorphous light eruption (PMLE)?What are the racial predilections of polymorphous light eruption (PMLE)?What are the sexual predilections of polymorphous light eruption (PMLE)?Which age groups have the highest prevalence of polymorphous light eruption (PMLE)?What is the prognosis of polymorphous light eruption (PMLE)?Which clinical history findings are characteristic of polymorphous light eruption (PMLE)?Which physical findings are characteristic of polymorphous light eruption (PMLE)?What are the physical findings of variants of polymorphous light eruption (PMLE)?Which conditions should be included in the differential diagnoses of polymorphous light eruption (PMLE)?What are the differential diagnoses for Polymorphous Light Eruption?What is the role of lab testing in the diagnosis of polymorphous light eruption (PMLE)?What is the role of phototesting in the diagnosis of polymorphous light eruption (PMLE)?Which histologic findings are characteristic of polymorphous light eruption (PMLE)?What roles do photoavoidance and sunscreen usage play in polymorphous light eruption (PMLE) treatment?What is the efficacy of phototherapy in the treatment of polymorphous light eruption (PMLE)?What is the role of antioxidants in the treatment of polymorphous light eruption (PMLE)?What is the role of vitamin therapy in the treatment of polymorphous light eruption (PMLE)?What is the role of steroids and antihistamines in the treatment of polymorphous light eruption (PMLE)?What is the role of antimalarials and beta-carotene in the treatment of polymorphous light eruption (PMLE)?What is the role of azathioprine in the treatment of polymorphous light eruption (PMLE)?What other therapies may be effective for treatment of polymorphous light eruption (PMLE)?How is polymorphous light eruption (PMLE) prevented?Which agents increase the effectiveness of sunscreen for the treatment of polymorphous light eruption (PMLE)?Which medications in the drug class Vitamins are used in the treatment of Polymorphous Light Eruption?Which medications in the drug class Immunomodulators are used in the treatment of Polymorphous Light Eruption?Which medications in the drug class Corticosteroids are used in the treatment of Polymorphous Light Eruption?Which medications in the drug class Antimalarials are used in the treatment of Polymorphous Light Eruption?

Author

Saud A Alobaida, MBBS, FRCPC, Dermatologist, Pediatric and General Dermatology, Department of Dermatology, King Faisal Specialist Hospital and Research Centre, Saudi Arabia

Disclosure: Nothing to disclose.

Coauthor(s)

Wingfield Rehmus, MD, MPH, Dermatologist, BC Children's Hospital, Vancouver, British Columbia

Disclosure: Serve(d) as a speaker or a member of a speakers bureau for: Abbvie; Valeant Canada<br/> Received honoraria from Valeant Canada for advisory board; Received honoraria from Pierre Fabre for advisory board; Received honoraria from Mustella for advisory board; Received honoraria from Abbvie for advisory board.

Specialty Editors

Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA

Disclosure: Nothing to disclose.

Jeffrey P Callen, MD, Professor of Medicine (Dermatology), Chief, Division of Dermatology, University of Louisville School of Medicine

Disclosure: Received income in an amount equal to or greater than $250 from: Biogen US (Adjudicator for study entry cutaneous lupus erythematosus); Priovant (Adjudicator for entry into a dermatomyositis study); IQVIA (Serono - adjudicator for a study of cutaneous LE) <br/>Received honoraria from UpToDate for author/editor; Received royalty from Elsevier for book author/editor; Received dividends from trust accounts, but I do not control these accounts, and have directed our managers to divest pharmaceutical stocks as is fiscally prudent from Stock holdings in various trust accounts include some pharmaceutical companies and device makers for these trust accounts for: Stocks held in various trust accounts: Allergen; Amgen; Pfizer; 3M; Johnson and Johnson; Merck; Abbott Laboratories; AbbVie; Procter and Gamble;; Celgene; Gilead; CVS; Walgreens; Bristol-Myers Squibb.

Chief Editor

Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Disclosure: Nothing to disclose.

Additional Contributors

Craig A Elmets, MD, Professor and Chair, Department of Dermatology, Director, Chemoprevention Program Director, Comprehensive Cancer Center, UAB Skin Diseases Research Center, University of Alabama at Birmingham School of Medicine

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: University of Alabama at Birmingham; University of Alabama Health Services Foundation<br/>Serve(d) as a speaker or a member of a speakers bureau for: Ferndale Laboratories<br/>Received research grant from: NIH, Veterans Administration, California Grape Assn<br/>Received consulting fee from Astellas for review panel membership; Received salary from Massachusetts Medical Society for employment; Received salary from UpToDate for employment. for: Astellas.

Noah S Scheinfeld, JD, MD, FAAD, † Assistant Clinical Professor, Department of Dermatology, Weil Cornell Medical College; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, New York Eye and Ear Infirmary; Assistant Attending Dermatologist, New York Presbyterian Hospital; Assistant Attending Dermatologist, Lenox Hill Hospital, North Shore-LIJ Health System; Private Practice

Disclosure: Nothing to disclose.

Raul Del Rosario, MD, Consulting Staff, Dermatopathology, Mission Hospital at Laguna Beach

Disclosure: Nothing to disclose.

Sophie Shirin, MD, Consulting Staff, Global Dermatology

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author, Dr. Ada Winkielman, to the development and writing of this article.

References

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Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MCJd/pmle-15.JPG).

Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MSJd/pmle-14.jpg).

Polymorphous light eruption on the arm. Courtesy of Waikato District Health Board and DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MCJd/pmle-22.JPG).

Polymorphous light eruption on the thighs and hand. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/reactions/pmle2.jpg).

Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-1.jpg).

Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-2.jpg).

Polymorphous light eruption pathology showing papillary dermal edema with lymphocytes in the epidermis (exocytosis). Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-3.jpg).

Polymorphous light eruption pathology. The infiltrate is mainly lymphocytic but there may be intermixed eosinophils, neutrophils, and histiocytes. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-4.jpg).

Photograph of a springtime eruption of polymorphous light eruption in a 6-year-old boy. The eruption has occurred in the spring since the patient was aged 5 years, and it resolves completely with no scarring by mid to late summer. High block sunscreens attenuate but do not prevent the eruption. No itching or pain occurs. Courtesy of Dr. Jeremy F. Harrison, FRCA, FFAEM.

Polymorphous light eruption on the thighs and hand. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/reactions/pmle2.jpg).

Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MSJd/pmle-14.jpg).

Polymorphous light eruption on the chest. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MCJd/pmle-15.JPG).

Polymorphous light eruption on the arm. Courtesy of Waikato District Health Board and DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/_resampled/FitWzY0MCw0ODBd/WatermarkedWyIyNTg0MCJd/pmle-22.JPG).

Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-1.jpg).

Polymorphous light eruption pathology showing papillary dermal edema. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-2.jpg).

Polymorphous light eruption pathology showing papillary dermal edema with lymphocytes in the epidermis (exocytosis). Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-3.jpg).

Polymorphous light eruption pathology. The infiltrate is mainly lymphocytic but there may be intermixed eosinophils, neutrophils, and histiocytes. Courtesy of DermNet New Zealand (https://www.dermnetnz.org/assets/Uploads/pathology/e/pmle-figure-4.jpg).