The role of histopathology in polymorphous light eruption light testing

Abstract

Summary Provocative light testing was performed in ten patients with polymorphous light eruption (Pmle) and in ten normal subjects to determine whether the histopathology of irradiated test sites could be used as an end point for a positive response. Three separate test sites on the lower back were irradiated (UV‐B) with a single exposure to i minimal erythema dose (MED), a single exposure to 5 x MED, or three consecutive daily exposures to 3 x MED. Biopsies of all test sites were coded and examined without knowing if the biopsy was from a normal subject or a patient with Pmle. In no case was a rash reproduced by light testing. A spectrum of histologic features were observed at the three test sites in both normal subjects and patients with Pmle with no significant differences noted between the two groups. It was concluded that the histology at these UV‐B irradiated test sites could not be used as an endpoint Pmle for testing. In establishing Pmle light testing techniques which rely on histology it is mandatory to include adequate numbers of normal controls.

The erythemal response to ultraviolet radiation in subjects with polymorphic light eruption

“…Although this phenomenon has been interpreted as an abnormal vesicular response (Jansen 1982), in our experience it is frequently observed in normal subjects whenever high enough doses of UV radiation are employed. In common with other workers (Tanenbaum et al, 1981) we attribute this appearance to perifollicular oedema and regard it as a normal response. The difference in the slopes of the dose-response curves for UV-C and UV-B erythema in normal subjects suggests that more than one mechanism is involved in the causation of ultraviolet erythema (Farr & Diffey, 1985).…”

Marked papillary dermal edema – an unreliable discriminator between polymorphous light eruption and lupus erythematosus or dermatomyositis

“…Descriptions of the histopathology seen in PMLE also have varied, in part because of the fact that various clinical morphologies have been reported to manifest differing microscopic attributes and in part because many reports have been based on experimentally produced lesions. 22,23 There are few primary reports of clinical lesions that arose spontaneously. 24 -27 Of these, Lamb et al described 28 patients with PMLE displaying four different clinical morphologies.…”

An Optimal Method for Experimental Provocation of Polymorphic Light Eruption

“…[26][27][28] This makes histologic interpretation difficult because of coexistent sunburn, which results in mononuclear cell infiltration. Even recent studies have used high doses to provoke a PLE reaction (3.3 MED of UV-B 19 ; 6 MED of UV-B 20 ; and 2-4 MED of UV-B or UV-A 29 ).…”