Ultraviolet-radiation suppresses cell-mediated immunity in healthy humans. It has been postulated that, in the short term, this immunosuppression prevents autoimmune responses to ultraviolet-radiation damaged skin. Patients with polymorphic light eruption (PLE) demonstrate abnormal responses to ultraviolet-radiation suggestive of an immune response to an ultraviolet-radiation-induced antigen. We investigated whether PLE patients (n=22) were resistant to ultraviolet-radiation-induced immunosuppression compared to skin-type, aged-matched controls (n=23). Groups of patients and controls (six subjects per group) received a single dose of solar-simulated ultraviolet-radiation of either 0, 0.6, 1 or 2 minimal erythema doses (MED). Erythema was quantified using a reflectance meter and all volunteers were sensitised on the irradiated site with dinitrochlorobenzene. Contact hypersensitivity responses (CHS) to dinitrochlorobenzene were quantified after challenge using ultrasound. Ultraviolet-radiation-induced erythema was comparable in patients and controls. CHS was comparable in unirradiated patients and controls. UVR-induced a dose-dependent suppression of CHS in all volunteers but patients were more resistant to immunosuppression after 1MED. Exposure to 1MED suppressed CHS by 78% in controls but induced less suppression in patients (44%, p < 0.01). Our data suggest that PLE patients have a flaw in their immunoregulatory response to ultraviolet-radiation it is only apparent over a narrow dose range around 1 MED.

This study has (i) validated the concept that a single score can reflect disease severity in PLE by showing that the principal characteristics of the condition, including, for example, the extent of anatomical distribution and the ease of provocation of the eruption, correlate with each other; (ii) formulated the PLESI, which is a simple, valid and reproducible way of assessing disease severity; we suggest it could be used worldwide to determine the severity of PLE among patients enrolled in future PLE research; (iii) shown that the ease with which the eruption is provoked by solar-simulated radiation correlates with the severity of the condition; and (iv) shown that the duration of persistence of the eruption after sun exposure does not correlate with the severity of the condition.

The Dutch Lymphoedema Quality-of-Life Questionnaire can be used for health-related quality-of-life research in lower limb lymphoedema patients.