Efficacy of short-course oral prednisolone in polymorphic light eruption: a randomized controlled trial

Polymorphic light eruption (PLE) is the most common so-called idiopathic photosensitivity disorder and affects up to 15% of the population in the U.K.; brief courses of systemic steroids have been tried and anecdotally have apparently been dramatically effective in the treatment of acute attacks.

To assess the efficacy and safety of a short course of moderate-dose oral prednisolone used from the earliest onset of the eruption in the treatment of PLE.

The study was double-blind placebo-controlled, all patients being given both prednisolone and placebo, but randomized to take either one or the other from the earliest sign of onset of rash; if within 48 h there was no improvement, they transferred to the other medication. Each participant also applied a broad-spectrum, highly protective sunscreen 2-hourly during sun exposure, continued his or her usual degree of exposure after any development of PLE, and kept a diary noting details of the eruption, amount of exposure, weather conditions and any adverse events. Statistical analysis was performed by means of the non-parametric log rank test based on Kaplan-Meier plots and bootstrapped confidence intervals (CIs) for the means, using the time in days for the itch and rash to clear as the end-points.

Twenty-one patients entered the study but only 10 required medication. Eight who took prednisolone first and remained on it or transferred to it from placebo all improved, with the itch settling fully within a mean 2.8 days of starting the prednisolone and the rash clearing by 4.2. In the two who took placebo first and remained on it, the itch took a mean 5.4 days to settle and the rash a mean 7.8. No patient who started with prednisolone changed to placebo. Thus, the prednisolone as randomized was better than placebo at settling both the itch (mean 2. 6 days less, CI 0.7-4.0, P = 0.015) and rash (mean 3.6 days less, CI 0.6-6.1, P = 0.036); only one patient experienced mild adverse effects of transient gastrointestinal upset and depressed mood.

The acute eruption of PLE is likely to respond rapidly to short courses of prednisolone therapy given from the earliest onset of the condition, and the treatment is safe.