Photosensitive atopic dermatitis--a neglected subset: Clinical, laboratory, histological and photobiological workup.

BACKGROUND

Photosensitive atopic dermatitis (PhAD) is a scarcely reported entity characterized clinically by a photodistributed rash in patients who fulfil the criteria for atopic dermatitis (AD).

OBJECTIVES

The aim of this retrospective study is to define significant clinical, laboratory and immunological parameters as well as photobiological features for diagnosing PhAD.

METHODS

We conducted a single-centre retrospective analysis of 17 patients with long-standing AD who in the disease course suddenly developed photosensitivity. All patients with suspected PhAD treated in our department between 2009 and 2014 were included in the study. Diagnostic methods were immunological parameters, prick and patch testing, histology and phototesting procedures.

RESULTS

Onset of photosensitivity was observed during spring, summer and during exposure to artificial UVR (Ultraviolet radiation) as part of the patients' treatment regimen. Symptoms appeared 31.5 months on average after AD diagnosis was established. Although the MED (Minimal erythematous dose) was normal compared to a control group, all patients tested with photoprovocation methods exhibited a positive reaction. Two types of reactions were observed: papular and eczematous reactions, both types having similar histology. The wavelength spectrum most commonly involved was UVA. The disease seems to affect women more often than men. Predilection sites included face, neck, exposed trunk areas and arms. Patients with PhAD had coexistent eczematous lesions in non-sun-exposed skin. IgE levels were elevated in 11/17 patients (65%), with a median value of 269 kU/L.

CONCLUSION

PhAD is an underreported subset of atopic dermatitis, which is rarely diagnosed. This study suggests that several features including atopic diathesis, eczematous lesions in UVR exposed body regions and positive photoprovocation reaction are suggestive of PhAD as the likely diagnosis. Typically, the atopic eczema starts without a sign of photosensitivity, however, in a subgroup of AD patients after a few months to years, a switch occurs leading to PhAD.