Skin photodynamic therapy in severe localized atopic dermatitis: a case report

Conflicts of interest: none declared. Madam, Skin photodynamic therapy (PDT) is a technique that combines the administration of porphyrins or porphyrin precursors and illumination with red or blue light at the diseased sites. Photosensitizers show the highest peak of absorption at about 405 nm, although a wavelength of about 635 nm is preferentially used for irradiation as light in the red part of the spectrum shows the best tissue penetration.1 Irradiated photosensitizers produce singlet oxygen, a highly reactive activated oxygen species and a major cytotoxin. The porphyrin precursor 5‐aminolaevulinic acid (ALA) or its methyl ester (methyl aminolaevulinate, so far the only approved formulation in Europe) is applied topically as photosensitizer to exclude systemic reactions. Possible light sources include lasers as well as incoherent light sources; irradiation with incoherent light sources is cheaper and more appropriate for large treatment areas. PDT appears to exert several favourable features for the treatment of localized skin diseases. Clinical conditions such as actinic keratoses, nodular and superficial basal cell carcinoma, skin tumours or precancerous lesions, Bowen disease, nonmalignant conditions such as acne vulgaris and leishmaniasis, as well as age‐related macular degeneration and ageing due to sun exposure have been treated with PDT.2, 3 The main advantages of PDT in comparison with other treatment modalities are its excellent cosmetic results and its high remission rates despite low invasiveness.3 Surprisingly, PDT has not been used in atopic dermatitis (AD) so far. In clinical practice patients with severe AD might be good candidates to receive a nontoxic treatment instead of local tacrolimus or systemic ciclosporin. We report an adult with AD, previously showing very severe localized disease, who responded favourably to PDT.