Treatment of polymorphic light eruption

Polymorphic light eruption (PLE) is a highly prevalent photosensitivity disorder, estimated to affect 11-21% people in temperate countries. Typically, PLE appears as a recurrent pruritic eruption comprising papules and/or vesicles and/or plaques, which occurs on photo-exposed skin sites following sun exposure, and which heals without scarring. Commoner in females, the aetiology is uncertain, although there is evidence of an immune basis. We perform a review of the prophylaxis and treatment of this condition. While sun protection, corticosteroids and desensitization phototherapy are the mainstays of management, a range of anti-inflammatory and immunomodulatory agents are reported.     

Hereditary polymorphic light eruption in Canadian Inuit

Twelve Canadian Inuit patients from the Keewatin District of the Northwest Territories were found to have hereditary polymorphic light eruption. The clinical manifestations were similar to those described in the North American Indian, with a photodermatitis occurring in the sunlight-exposed area. The onset occurred prior to the age of 15 years in 70% of subjects, and the condition was seasonally recurrent, starting in February and lasting until September. Patients demonstrated improvement on a combined regime of local therapy and oral trioxalen. Seventy-five percent of patients had a family history of photosensitivity, suggesting an autosomal dominant trait with incomplete penetrance. Indian ancestry was not demonstrated in these patients.     

Controlled therapeutic trials in polymorphic light eruption

A series of controlled trials of treatments for polymorphic light eruption (PLE) with oral beta-carotene, ketoprofen and chloroquine, and topical benzimidazole sunscreen cream is described. Clinical features were recorded using diary cards filled out by the patients, and exposure to UVR was measured individually in all patients with film badges. Symptoms were found to be dependent on exposure. None of the treatments proved very effective, but beta-carotene seemed to give significant slight protection against irritation and erythema, though this was not confirmed in a repeat study using a higher dose. Chloroquine seemed to protect slightly against irritation. As the degree of improvement with chloroquine and beta carotene is quite small, equivalent to a protection factor of 2, it is arguable whether these treatments as used here are worthwhile and in the case of chloroquine, with its risk of adverse side effects, whether it is justifiable. Other treatment and dose regimes are possible and further trials seem worthwhile. Our studies have helped to define the special difficulties in collecting objective data in PLE and should improve the methods for assessing treatment in the photodermatoses.     

Serum antioxidant capacity in polymorphic light eruption

Polymorphic light eruption is one of the few dermatological diseases in which some antioxidants have been said to be reduced in both the epidermis and the blood. This study measured the hydrosoluble antioxidant capacity in the serum of patients with polymorphic light eruption, using a commercially available kit. All patients were tested in winter, in order to avoid the influence of exposure to ultraviolet light. The results showed that a hydrosoluble antioxidant capacity was significantly decreased (by 29%) in patients with polymorphic light eruption, and b) that females (both patients and controls) has less hydrosoluble antioxidant capacity (by 27%) than males. In addition, the hydrosoluble antioxidant capacity values for females with polymorphic light eruption increased significantly with age, possibly accounting for the well-known propensity of young women to polymorphic light eruption. These last observations have not been reported previously.     

Milia complicating bullous polymorphic light eruption

Polymorphic light eruption (PLE) is the most common photosensitivity disorder. Typically, PLE manifests in the spring or summer months as a recurrent pruritic papular and/or vesicular eruption occurring on photoexposed skin areas following sun exposure. The milia are caused by proliferative tendencies of the epithelium after injury. These may occur in areas of subepidermal bullous eruption. We report an original case of bullous PLE complicated by milia. Such association has not been reported previously.     

The heritability of polymorphic light eruption

Polymorphic light eruption is classified as an acquired idiopathic photodermatosis, yet it appears to cluster in families, suggesting a possible genetic component. In this study, we assess the heritability of polymorphic light eruption using the classical twin model. Polymorphic light eruption was investigated by a nurse-administered questionnaire in a sample of 420 pairs of adult female twins from St Thomas' Hospital UK Adult Twin Registry, including 119 monozygotic and 301 dizygotic pairs. Probandwise concordance for the presence and absence of disease was calculated and the heritability of polymorphic light eruption assessed by a quantitative genetic model fitting approach using Mx software. The prevalence of polymorphic light eruption was 21% and 18% in monozygotic and dizygotic twins, respectively. A family history of polymorphic light eruption in first-degree relatives (not including the cotwin) was present in 12% of affected twin pairs (where at least one twin had polymorphic light eruption) compared with 4% of unaffected twin pairs, providing evidence of familial clustering (p < 0.0001). The probandwise concordance for polymorphic light eruption was higher in monozygotic (0.72) than in dizygotic twin pairs (0.30), indicating a strong genetic effect. Quantitative genetic modeling found that a model comprising additive genetic (A) and unique environmental (E) factors provided the most parsimonious fit, although a dominant gene effect could also explain our data. In the AE model, 84% (95% confidence interval 65-94%) of the variance in susceptibility to polymorphic light eruption is attributed to additive genetic factors with the remaining 16% (95% confidence interval 6-35%) to unique environmental effects. These data establish a clear genetic influence in the expression of polymorphic light eruption and provide a basis for examining candidate genes that may be pathogenic in this common condition.     

The actinic cheilitis of hereditary polymorphic light eruption.

Sixty-four North American Indians with hereditary polymorphic light eruption (HPLE), or a family history of HPLE, had chronic, recurrent, exudative, and exfoliative cheilitis. Fifty-two had the cheilitis by the age of 10 years. Microscopically, the epithelium was either thickened, or thinned and covered by a thick crust. The dermis had a dense infiltration of inflammatory cells, mostly lymphocytes and plasma cells. The condition was not premalignant. The HPLE has to be differentiated from the chronic actinic cheilitis caused by long exposure to sunlight with out any element of hypersensitivity. The latter is potentially premalignant. Chronic recurrent actinic cheilitis associated with hereditary polymorphic light eruption appears to be a specific characteristic of photosensitivity occurring in American Indians. Plasma cell infiltration is not specific for either type of cheilitis.     

A study on cell-mediated immunity in polymorphic light eruption

Polymorphic light eruption (PLE) can be defined as a delayed abnormal response to sunlight. In this paper some features of the presumable immune response were studied in 55 patients with PLE and the results were compared with the findings available in 58 cases with porphyria cutanea tarda (PCT). The mean intracutaneous reactivity index measured by skin tests of delayed type was normal in both diseases. The number of the active and total E-rosette-forming peripheral lymphocytes was significantly lower in the active stage of PLE whereas in remission normal values were found. In active PCT only the number of the total E-rosette-forming cells was decreased. The percentage of lymphocytes with so-called dot-like alpha-naphthyl acetate esterase enzyme reaction was reduced significantly in the active stage of PLE whereas in remission their number was normal. Changes observed in PLE seem to be functional and suggest the involvement of T lymphocytes in some phases of the hypersensitive cutaneous reaction induced by sunlight.     

In vitro lymphocyte studies in chronic polymorphic light eruption

Lymphocytes suspended in autologous sera from seven subjects with chronic polymorphic light eruption were irradiated with UV radiation corresponding to the peak of their action spectra, and lymphocyte transformation and migration inhibition studies were subsequently carried out. The results obtained do not support a concept of photoallergy, but an increased thymidine uptake ratio was obtained in one subject, the only one who had shown clinical involvement of covered skin sites in addition to light exposed ones.