Author(s): Albert Wolkerstorfer [[dagger]â ] 1 , Elian EA Brenninkmeijer 2
308-nm phototherapy; atopic dermatitis; excimer laser; prurigo
Prurigo nodularis through the years
The term prurigo, originating from pruire (itching), was coined by Ferdinand von Hebra in 1850, characterizing typical itching papules and nodules induced by scratching  . Since then, various eponyms have arisen. Ernest Henri Besnier (1860) described a chronic lichenoid flexural form of atopic dermatitis still known as prurigo of Besnier  . In 1909, Hyde described an intractable chronic eruption characterized by numerous persistent pruritic nodules, mainly on the extremities [1,3] . To date, Hyde'âs prurigo or prurigo nodularis is the genuine chronic form of prurigo  . Prurigo nodularis is generally regarded as a variety of eczema; in many cases there is a history of atopic dermatitis. Prurigo nodularis can be associated with an atopic background; 60-â80% of patients with prurigo nodularis are atopic and up to 46% have atopic dermatitis [3,5] . The atopic type of prurigo nodularis or prurigo form of atopic dermatitis is accompanied by cutaneous hypersensitivity to environmental allergens with the presence of allergen-specific IgE  .
Prurigo nodularis: a difficult disease to treat
The prurigo form of atopic dermatitis often represents a therapeutic challenge; most cases of the prurigo form of atopic dermatitis are therapy resistant and patients will be subjected to various types of treatment. Topical treatments include corticosteroids, coal tar and bath phototherapy. Systemic treatments include cyclosporine, chloroquine, naltrexone, dapsone, thalidomide and photochemotherapy (PUVA). Today, narrowband 311-nm ultraviolet B (NB-UVB) phototherapy is widely recognized as an effective treatment modality for patients with chronic atopic dermatitis  .
The benefit of conventional phototherapy is limited in prurigo nodularis
Narrowband 311-nm ultraviolet B phototherapy is effective against moderate-to-severe atopic dermatitis, and is well tolerated by most patients [7,8] . The main disadvantage of photo(chemo)therapy is that the whole body surface is exposed to UV radiation, and not merely the affected areas. In patients with lesions restricted to relatively small surface areas, such as in prurigo nodularis, a targeted NB-UVB therapy is required.
Targeted UVB therapy: the excimer laser for localized inflammatory skin disorders
In contrast to conventional phototherapy, the excimer laser offers the opportunity to selectively direct treatment to lesional skin using high doses of UVB. The excimer laser was invented in 1970 and introduced for eye surgery in 1981. In 1997, the 308-nm xenon chloride (XeCl) excimer laser was introduced for the treatment of psoriasis  . Afterwards, an increasing number of indications were reported to improve by such a treatment. For localized psoriasis vulgaris, the excimer laser was found to be more effective than NB-UVB  . The main advantages of the excimer laser were comparable or higher efficacy with fewer treatments...