Photosensitivity in atopic dermatitis: demonstration of abnormal response to UVB

Throwing a light on photosensitivity in atopic dermatitis: a retrospective study

BACKGROUND

Photosensitivity in atopic dermatitis (AD) is a well known but ill-defined phenomenon.

OBJECTIVES

To determine the prevalence of photosensitivity in patients with AD, define its clinical characteristics, and analyze the photo provocation test (phototest) results.

METHODS

A retrospective study of patients with AD who were phototested because of suspected photosensitivity at our department during the period 1994-2004.

RESULTS

The total number of patients with AD seen in our department between 1994 and 2004 was 3804, of whom 145 patients (45 men and 100 women) were phototested. Photosensitivity was confirmed in 108 (74%) of these 145 patients (33 men and 75 women). The minimal erythema dose (MED) for UVB was decreased in eight of these 108 patients (7%) and the MED for UVA in five patients (5%). Two major clinical reaction patterns were observed: a polymorphic light eruption-type reaction in 51 patients (47%) and an eczematous reaction in 44 patients (41%). Seventy-two of the 108 patients (67%) had a pathologic reaction to UVA and UVB, 18 patients (17%) were only UVB sensitive, and 18 patients (17%) were only UVA sensitive. Photopatch tests were performed in 125 patients (86%). Twenty-nine patients (23%) had a positive photocontact reaction to one or more substances.

CONCLUSION

Photosensitivity is found in approximately 3% of patients with AD and the majority are female. Photosensitivity in patients with AD consists of two clinical reaction patterns distinguishable by phototesting. Patients were diagnosed with either AD and co-existing polymorphic light eruption or photosensitive AD.

Optimized UVB Treatment of Atopic Dermatitis Using Skin Reflectance Measurements. A Controlled, Left–Right Comparison Trial

In a randomized, open, left-right comparison study, 20 patients with atopic dermatitis were treated with UVB. One side of the body received UVB in a conventional regimen with fixed dosage increments, the other side was given UVB dosages according to skin reflectance measurements of skin pigmentation and erythema. Clinical outcome was assessed by SCORAD. The initial, final and cumulative UVB dosages, time to 50% reduction in SCORAD, and side effects were compared. The initial UVB dosage was somewhat higher in the skin reflectance-guided treatment than in the conventional UVB regimen, although not significantly. There was no difference in the reduction of SCORAD comparing the two treatment options; however, the final UVB dosage and the cumulative UVB dosages were significantly lower in the optimized regimen. This new technique offers the same therapeutic advantage and security as a dose regimen guided by minimal erythema dose testing. However, measurement of skin pigmentation by skin reflectance is a rapid method, which can easily be operated by nurses.

The idiopathic photodermatoses

The idiopathic photodermatoses present a challenge for dermatologists. Although, as in other specialty areas, the classical clinical presentation produces few problems, it is the severe forms and overlap cases that cause the most difficulty. It is fortunate that the semi-objective investigation of phototesting is available, which, when conducted carefully, reveals so much about the nature of this group of conditions. This essential investigation not only helps achieve a diagnosis, but also affords material for study and a means of monitoring therapy response or progress towards spontaneous resolution. Although these conditions are grouped together, throughout this century we have seen a continuing process of distinct diseases emerging as a consequence of careful clinical observation and investigation.

A variety of skin responses to ultraviolet irradiation in patients with atopic dermatitis

Skin responses to ultraviolet irradiation in patients with atopic dermatitis were studied to evaluate the role of sunlight in the exacerbation of atopic dermatitis. A total of 15 patients, seven males and eight females, with atopic dermatitis who complained of exacerbation of their dermatitis after sun exposure were examined by photo testing with UVB and UVA irradiation and photopatch tests. Nine out of 15 patients showed abnormal skin reactions. Lowered minimal erythema doses (MEDs) to a single exposure of UVB, papular or erythematous responses after single or repeated exposures to UVB or UVA and positive photopatch test reactions to sunscreen ingredients and fragrances were found. There are apparently multiple mechanisms of photoexacerbation in patients with atopic dermatitis.

A UVB phototherapy protocol with very low dose increments as a treatment of atopic dermatitis

From 1991 to 1992, 15 patients with atopic dermatitis were treated with a new UVB treatment regimen guided by skin reflectance measurements. The new treatment was characterized by very low dose increments from start to end of therapy. The median cumulative dose increment during therapy was only 20%. The severity of the disease, the efficacy of the treatment, the occurrence of adverse effects and the cumulative UVB dose were obtained from the case records. This data were compared in an open study with the data obtained from 17 patients with atopic dermatitis who were treated from 1988 to 1991 at the department with a standard UVB treatment regimen with stepwise dose increments. There was no difference in the severity of the disease at the beginning of the therapy between the two groups. The skin reflectance-guided low-dose UVB therapy was not significantly faster (3.5 weeks) than the regimen with stepwise dose increments (4.5 weeks). The cumulative UV exposure was four times lower with the new treatment regimen (34 standard erythema doses) compared with the old regimen (161 standard erythema doses), P<0.001. The healing score was significantly higher with the new treatment regimen compared with the old, P<0.05. This study indicates that skin reflectance-guided UVB phototherapy may enable the dermatologist to lower the cumulative UVB exposure significantly without losing effect.

Atopic dermatitis: triggering factors

Atopic dermatitis is a hereditary disorder, frequently associated with allergic rhinitis and bronchial asthma. The disease may be influenced by many triggering factors such as irritants, aeroallergens, food, microbial organisms, sex hormones, stress factors, sweating, and climatologic factors. Moreover, it is important to be aware of contact allergy as a complicating factor. This review deals with recent clinical, experimental, and some therapeutic data on these triggering factors.

Atopic dermatitis: recent trends in pathogenesis and therapy

Emerging concepts in the areas related to the pathogenesis and treatment of atopic dermatitis are reviewed. In particular, recent findings have revealed several key steps in the maintenance of a vicious circle of spongiotic dermatitis associated with elevated T-lymphocyte activation, hyperstimulatory Langerhans cells, defective cell-mediated immunity, and B-cell IgE overproduction. The discovery of specific IgE-binding structures on Langerhans cells provides a mechanism for Langerhans cells to capture and present IgE-targeted allergens to allergen-specific T cells. Furthermore, certain microbial allergens that tend to preferentially elicit IgE-type responses also elicit a T-cell response dominated by the IgE-inducing lymphokine interleukin 4. Repeated stimulation by activated Langerhans cells appears to induce just such a response. Abnormal biochemical responsiveness and mediator release by AD monocytes, mast cells, and eosinophils also participate in the sustainment or initiation of such a vicious circle, and contribute directly to the dermatitis as well. Developments in the areas of neuropeptides, genetics, microbial superantigens, and cytokine networks in the skin also appear to have promise in providing a rational link between immune defects and the inflammatory events in AD. Conventional therapy remains the mainstay of atopic dermatitis management; however, new therapies based upon the above concepts are being tested in clinical trials. Although the difficulty of objectively grading AD lesional activity and the high placebo response of AD patients hampers the interpretation of many reports, several types of approaches are coming into focus. The effectiveness of cyclosporin A, which targets T-cell activation and antigen presentation, indicates that additional agents with such activity should be effective, and verifies the criticality of these cells in AD pathogenesis. Therapy with biologic response modifiers, such as interferon gamma or thymopentin, is oriented toward normalization of imbalanced immune responsiveness, rather than direct suppression of the immune system. The mechanism of action of and toxicities of Chinese herbal mixtures require further investigation, but may reveal hitherto unconsidered avenues. Other recent therapeutic trials have focused on reduction of trigger factors, such as house dust mite exposure, foods, and the abnormal epidermal lipid barrier to irritation.