Polymorphous Light Eruption 

Updated: Jan 22, 2020
Author: Saud A Alobaida, MBBS, FRCPC; Chief Editor: Dirk M Elston, MD 



Polymorphous 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. Within any single patient, only one clinical form is consistently manifested. The word polymorphous in the name refers to the different morphologic presentation of the condition.

PMLE engenders a substantial psychosocial impact. In a review by Richards et al, up to 40% of patients described emotional distress related to PMLE.[1] Women associated more severe consequences linked to PMLE and were more emotionally distressed than men. Patients experience a decrease in quality of life owing to 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 hat wear. Photohardening is beneficial and can be used early in spring to increase tolerance to sun exposure. Topical and systemic immunosuppressants are used for symptom management. Their use should be tailored to each patient where the benefits and risks are weighted.

The possibility that a subset of PMLE called benign summer light eruption (BSLE), which might be milder and might be more ultraviolet (UV)–A driven, has been suggested by an Italian group.[2]

Note the images below.

Polymorphous light eruption on the thighs and hand 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 arm. Courtesy o 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).


The etiology of polymorphous light eruption (PMLE) is not fully known, and it is likely to be multifactorial. The appearance in families supports a genetic association. 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]

PMLE clusters in families, suggesting a genetic component. In a study by Millard et al, they studied 420 pair of adult twins and found that 21% of monozygotic and 18% of dizygotic twins had PMLE.[4] First-degree family history was seen in 12% compared with 4% of unaffected twins. The prevalence of PMLE in first-degree family members is seen in 20.9% of members.[5]

Actinic prurigo (AP) is thought to be a subtype of PMLE, given that they share 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. HLA-DR4 is strongly associated with AP.[6]

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.[7, 8]

Kölgen et al noted that the reduced expression of tumor necrosis factor-alpha, 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.[9] 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.[10]

A study by Koulu et al assessed 48 subjects (24 patients with PMLE and 24 healthy sex-matched and age-matched controls).[11] The study found similar immunosuppression of contact sensitization to diphenylcyclopropenone due to earlier exposure to solar-simulating UV radiation between both groups. However, among patients with PMLE who were immunosuppressed by UV radiation, only one exhibited immunotolerance to the same allergen 10-24 months later (P = .023). 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 PMLE skin after UVB irradiation compared with healthy case control subjects (P< .05).[12] Intercellular adhesion molecule 1 (ICAM-1) and E-selectin expression on endothelial cells increased in both healthy controls and in the PMLE patients after UVB 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 UVB irradiation.

Apoptotic keratinocyte 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.[13] 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.[14, 15]

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, by antimicrobial peptide (AMP) release and activation of the innate immune system. A unique pattern of AMP was seen in PMLE patients when compared with patients with atopic dermatitis, psoriasis, or normal skin. An increase in psoriasin, RNAse7, human beta defensin-2 (HBD‐2), and LL37 are seen in PMLE, similar to psoriasis. However, PMLE patients had a lower level of HBD-3 compared with psoriasis and atopic dermatitis patients.[10, 16]

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.[17]

In some PMLE lesions induced by UVA, keratinocytes were found to express ICAM-1.[18, 19] 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.

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.[20]

Some have suggested that glutathione S-transferases (GSTs) act to protect against PMLE, but a study of the isoenzymes of the GST genes GSTM1, GSTT1, and GSTP1 found no protective relationship of these isoenzymes to PMLE.[21]

It is possible that the use of tobacco makes PMLE worse.[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 the patients. However, Native Americans have a hereditary form of PMLE with apparent autosomal dominant inheritance; 75% reveal disease in a family member.[24]



United States

Polymorphous light eruption (PMLE) affects about 10-20% of the US and Western Europe population.[25] This figure is likely to be an underestimate because many patients do not seek medical attention. Additionally, many of the photodermatoses were previously 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).

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 used a questionnaire to survey 4899 residents (49% men and 51% women) from randomly selected Chinese villages in several counties at different altitudes and with different ethnic majorities.[27] 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/day. The mean duration of PMLE was 5.8 years.[27]

A report from India in 2013 notes that PMLE is the most common photodermatitis after chronic actinic dermatitis, while hydroa vacciniforme and solar urticaria are uncommon.[28] Furthermore, this report stated lichenoid PMLE and pinpoint papular PMLE are the most common types found in the subcontinent.


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.[29, 30]

In a study of 280 American patients with photodermatoses,[31] 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.

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 PMLE was present in 54% and 86.2%, respectively (P< .0001)[32] ; thus, the researchers suggested that PMLE occurs more frequently in African Americans.


PMLE affects females 2-3 times more often than males. However, these data may be skewed because females are more likely to seek medical attention than males.


PMLE usually has an onset in the first three decades of life. Onset during childhood and late adulthood can be seen. Men seem to have later onset of the disease than women.

Studies have reported mean ages of 26.4 years and 37.8 years in their respective cohorts.[33, 34]


Expression of polymorphous light eruption (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 can reach up to 30 years.

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.




Polymorphous light eruption (PMLE) tends to manifest in the spring and early summer, or in the wintertime involving the face by reflected sunlight off snow.[35] In addition, PMLE is a recurrent condition and patients state they have had the eruption before and that it went away as time passed.

Typically, the lesions of PMLE first erupt after exposure to strong sun following a period of relative photoprotection such as 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. To trigger the eruption, it takes 30 minutes to several hours of sun exposure. The rash appears within hours to days of exposure, and it subsides over the next 1-7 days without scarring, although it has been reported to persist for up to 5 weeks.[36] Sun-exposed skin, especially that normally covered in winter (eg, upper chest, arms), is primarily affected, but autosensitization may lead to a generalized involvement. 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.

Jansen traced the natural history of chronic PMLE for 10.5 years in 138 people,[34] 85 of whom were female. In 57% of cases, the PMLE happened in a rapid fashion. Lesions often began in a small photoexposed area and extended to a greater area each year. Light sensitivity tended to increase with each subsequent year. 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.[34]

Physical Examination

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 (most common), plaques, papulovesicles, and eczematous 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. Note the images below.

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

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 (AP) is a more likely cause of the inflammatory photosensitivity disorder. Cheilitis is more common in the tropics and might be the only manifestation of the PMLE. In the case of photosensitive cheilitis, PMLE must be distinguished from chronic actinic cheilitis and 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), solar purpura, juvenile spring eruption (JSE), localized PMLE, scar PMLE, and PMLE sine eruption.

The pinpoint variant seems to be observed in patients with Fitzpatrick skin types IV-VI.[30] African Americans present with pinpoint papules (1-2 mm) that can be observed on sun-exposed areas, sparing the face and flexural surfaces.[37] It has also been described in a series from Singapore[38] and in a series of 34 Taiwanese patients whose rash resolved with sun protection.[29] Ten of these Taiwanese patients had mild spongiosis on biopsy.

BSLE presents with 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.

PMLE sin eruption presents with no visible lesions but symptoms of pain or pruritus upon exposure to UV light.

In a retrospective study from Spain in 2013,[39] 5 men and 4 women were suggested to have a localized variant of PMLE, termed ”spring and summer eruption of the elbows" by the authors. The mechanism that confined the lesions to these specific areas was not determined.

Scar PMLE that can occur on hypopigmented scars has been noted in India.[40]



Diagnostic Considerations

Some physicians regard actinic prurigo (AP) as a distinct photodermatosis, and other physicians consider it an insidiously developing, markedly excoriated variant of polymorphous light eruption (PMLE). AP is characterized by a high incidence of atopy and familial predisposition. It is likely to involve covered skin.

Chronic actinic dermatitis is a term that encompasses several syndromes previously considered separate entities (ie, actinic reticuloid, persistent light reactivity, photosensitive eczema, photosensitivity dermatitis)’ however, now they are considered variants of the same condition. Clinically, lesions are usually more eczematous and infiltrated than in PMLE and involve mostly exposed skin, but they may generalize to erythroderma. The actinic reticuloid form of chronic actinic dermatitis has a histologic pattern that resembles cutaneous lymphoma, with CD8+ cells predominating. The minimal erythema dose (MED) to UVB, and sometimes UVA, is reduced.

Solar urticaria represents an immediate hypersensitivity response to UV radiation. Characteristic whealing may be accompanied by systemic symptoms of faintness, nausea, and bronchospasm.

A novel condition resembling PMLE and effecting the face and body has been reported under the name “prolonged exposure dermatosis.” It has clinical and histologic findings similar to PMLE, and it has been reported to occur during a winter wilderness expedition.[41] Its clinical basis needs more explication.

A 2010 study by Gronhagen et al reported on the importance of differentiating systemic lupus and cutaneous lupus erythematosus from PMLE.[42] In this study, 23% of 260 systemic lupus erythematosus patients had cutaneous lupus erythematosus, and a history of PMLE was found in 42%. The history of PMLE can proceed the typical eruption of cutaneous lupus erythematosus.

Differential Diagnoses



Approach Considerations

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

Laboratory Studies

In polymorphous light eruption (PMLE), laboratory tests can be performed to rule out other dermatoses 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.[43]

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

Other Tests

Results of phototesting in polymorphous light eruption (PMLE) patients are controversial, ranging from an ability to reproduce the eruption by repeat phototesting in 60-100% of patients to an inability to do so, except in patients who are very photosensitive.[44] These differences may be explained by a lack of a 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

Perform repetitive light testing; irradiating three times the MED to UVA on the right forearm and three times the MED to UVB on the left forearm for 3 consecutive days. Results are read immediately, at 24 hours, and at 72 hours. A delayed reading at 1 week may also be helpful. The test results are often positive in PMLE. A negative result does not exclude the diagnosis. If a lesion (eg, papule, vesicle) develops, biopsy confirmation can be performed. 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. One of the two strips is exposed to UVA radiation 24 hours later. Both the irradiated site and the unirradiated site are read at 24, 48, and 96 hours. A positive reaction at the irradiated site but not at the unirradiated patch test site is diagnostic of a photocontact allergy. Positive reactions at both the irradiated site and the unirradiated site are indicative of a contact allergy. According to Leroy et al in 2002,[45] polychromatic phototesting seems to be more sensitive than UVA phototesting to assess PMLE, and results suggest UVB is a key trigger of PMLE.

Histologic Findings

The most striking feature of the biopsy specimen from a patient with polymorphous light eruption (PMLE) is edema in the upper part of the dermis. Tight, perivascular lymphocytic infiltrate is observed in the upper and mid 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. The dominant cell, however, is the lymphocyte. Mucin, which is thought to distinguish PMLE from lupus, can be present in skin biopsies of PMLE patients. A study of dermal mucin from lupus samples found that it is not so much different from that found in PMLE in comparison with other dermatitides, which also had some, but less, mucin (eg, erythema multiforme, fixed drug eruption, graft versus host disease, lichen planus, photodamaged skin).[46] 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 pathological features, but the history and location of the lesions can usually help make the diagnosis.

Note the images below.

Polymorphous light eruption pathology showing papi 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 papi 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 papi 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 infiltr 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).


Medical Care

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

DeLeo et al reported that sunscreen with 4 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.[47] Other studies support the use of UVA blockers to help prevent PMLE,[48] including a report that describes a lower percentage of PMLE (0% at 2 mg/m2; 33% at 1 mg/m2) in subjects who used high UVA sunscreen protection versus those who used lower UVA sunscreen protection (73% at 2 mg/m2; 80% at 1 mg/m2).[49]

Owing to the tendency of patients to experience hardening, phototherapy with UVA1, narrowband UVB, psoralen plus UVA (PUVA), or broadband UVB can harden the skin against the development of PMLE. A case of PMLE that failed UVA1 therapy has been reported[41] ; a woman aged 37 years developed a recalcitrant PMLE that lasted 5 weeks after completion of UVA1 phototherapy. Treatment given at the beginning of spring for several weeks may prevent flare-ups throughout the summer. PUVA was found to be superior to UVB in several studies, controlling the outbreaks in 90% of patients.[50] In another study of 25 patients with severe PMLE, narrowband UVB (311 nm) was found to be an equally effective alternative to PUVA.[51] Oral prednisone may be useful in conjunction with phototherapy to avoid eruption during therapy. Barolet and Boucher report on the use of light-emitting diode nonthermal therapy as a prophylactic measure for PMLE.[51]

Antioxidants have also been suggested to help prevent PMLE lesions. In a randomized, double-blinded, placebo-controlled clinical study by Hadshiew et al,[52] the efficacy of a new topical formulation was compared with a broad-spectrum sunscreen. 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. The authors found a statistically significant difference (P< .001) between the antioxidant-containing formulations and placebo and between the sunscreen-only formulation. 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 is far more effective in preventing PMLE than sunscreen alone. Also see Sunscreens and Photoprotection.

The use of topical antioxidants like 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.[53]

Some authorities believe that vitamin therapy is helpful in the treatment of PMLE. Nicotinamide was successful in 60% of 42 patients treated with 3 g/d orally for 2 weeks.[54] The rationale for its use 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.[53]

Systemic vitamin C and vitamin E do not prevent photoprovocation test reactions in persons with PMLE.[55]

The effect of topical calcipotriol (an analog of calcitriol, 1,25-dihydroxyvitamin D3) was described by Gruber-Wackernagle et al.[56] They evaluated the preventive effect of topical calcipotriol in a randomized, double-blinded, placebo-controlled, intraindividual half-body trial. 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. The authors used a specific PMLE test score based on affected area, skin infiltration, and pruritus to rate symptom severity at 48, 72, and 144 hours after the first photoprovocation exposure. They found pretreatment with calcipotriol, compared with placebo, significantly reduced PMLE symptoms on average by 32% (P = .0022), suggesting a possible benefit from prophylactic use of topical 1,25-dihydroxyvitamin D3 analogs in patients with PMLE.

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 patients prophylactically going on vacation or for those patients experiencing other unavoidable sun exposure.

Antihistamines may help with pruritus.

Antimalarials at low doses are sometimes helpful, especially in patients with a large papular variety of PMLE. 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.[57]

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 qd).[58] Both offered full sun tolerance in an equal but small percentage of patients when compared to a placebo.

Azathioprine was reported to be effective in two cases of recalcitrant severe disease at 0.8-2.5 mg/kg/d for 3 months.[59] In one patient, the effect lasted up to 4 months after the discontinuation of therapy. However, the limited available data and azathioprine toxicity should necessitate extreme caution if choosing this form of treatment.

Other therapies like cyclosporine can be helpful, but further studies are needed to determine their benefits.[14]

Interest in the use of thalidomide for a number of dermatoses (eg, Behçet syndrome, cutaneous lupus, porphyria cutanea tarda, PMLE) is reemerging. The immunomodulatory action on subsets of T cells was proposed. Thalidomide (50-200 mg PO qhs) has reportedly been very effective for Native American patients with PMLE. The most commonly described adverse effects with thalidomide are 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. The dose ranged from 720-1200 mg daily based on weight. It was protective in 30% and 28% of patients for UVA and UVB induced PMLE, respectively.[60, 61]

Afamelanotide helps in symptoms of PMLE by increasing the pigment in the skin, and it could be photoprotective for some patients.[62] Afamelanotide is injected subcutaneously at a dose of 20 mg, with slow release. This leads to increase in melanization in sun-exposed skin.


Avoiding sunlight during the hours of most intense UV irradiation (from 10 am to 2 pm) and wearing protective clothing (eg, hats, gloves, long pants, long sleeves) should be emphasized to polymorphous light eruption (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 preparation of sunscreen provides clinical benefit to patients with PMLE compared with sunscreens containing either ecamsule or avobenzone alone; each UVA filter individually.[48]



Medication Summary

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


Class Summary

These agents may have immunomodulatory effects.

Hydroxychloroquine (Plaquenil)

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

Prednisone (Deltasone, Meticorten, Orasone)

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 modify the activity of key factors in the immune system.

Thalidomide (Thalomid)

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 are essential for normal DNA synthesis and cell function.

Beta carotene

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)

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


Questions & Answers


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?