About three-quarters of patients acquire PLE after UV-A exposure only, one-tenth after UV-B exposure only, and the rest after a combination of UV-A and UV-B exposure.People vary in the amount of sun exposure needed to trigger the rash. Oxidative stress
Oxidative stress and the modification of the redox status of the skin has been implicated in the expression of PLE. Photosensitizer
It has been suggested that an undefined endogenous or exogenous photo-allergen may trigger a delayed immune reaction resulting in PLE. Genetics
Half of patients have a family history of PLE, demonstrating a clear genetic influence. Oestrogen effect
The preponderance in women with a decline in severity following menopause has been thought to be associated with oestrogen effects, A natural fall in oestrogens may account for the tendency to remit after the menopause. Diagnosis
The diagnosis of PLE is typically made by assessing the history and clinical observations. Any investigations are usually to exclude other conditions, particularly lupus and porphyria.Blood tests are usually normal. However, positive antinuclear antibody and extractable nuclear antigen (anti-Ro/La) in low titre may be found, even in the absence of other criteria to suggest a diagnosis of lupus erythematosus. If clinical findings suggest a possibility of porphyria, urinary and red cell porphyrin screening may be performed and are negative in PLE.Photoprovocation tests are usually not required but may be undertaken by specialised centres in winter.
Polymorphous light eruption (PLE), sometimes also called polymorphic light eruption (PMLE), is a non-life-threatening and potentially distressing skin condition that is triggered by sunlight and artificial UV exposure in a genetically susceptible person, particularly in temperate climates during the spring and early summer. Due to its many clinical appearances, it is named polymorphic or polymorphous and the terms are used interchangeably. The resulting itch can cause significant suffering.PLE is also defined as an idiopathic primary photodermatosis, in which the photosensitizer is unknown.Treatments include prevention with sun avoidance and supervised light therapy, and symptom control with topical steroids. Signs and symptoms
Typically, the first episode develops in the spring following the first exposure to intense sun. Further episodes of the irritable rash occur several hours to days following subsequent sun exposure.PLE appears on areas of the skin newly exposed to sunlight such as the visible part of the neckline, backs of hands, arms and legs, and feet, but less commonly the face. At these areas, there may be feelings of burning and severe itching. Smooth red-topped small papules which merge into plaques, small fluid-filled blisters (papulovesicles) and less commonly target-shaped lesions which look like erythema multiforme may be visible.