Exploring Clinical, Diagnostic Features of Photoaggravated Atopic Dermatitis

Diagnostic confirmation of photoaggravated atopic dermatitis (PAD) via phototesting may lead to improved clinical outcomes among patients, who experience a significant quality of life (QOL) burden from PAD.

Published recently in JAMA Dermatology, researchers sought to investigate the clinical and photobiological characteristics of PAD, a poorly understood subtype of AD that is exacerbated by ultraviolet radiation (UVR). An estimated 1.4% to 16% of patients with AD are affected by this disease subtype, although available studies focusing on the condition are scarce.

A case series study of cross-sectional data collected from 120 consecutive patients diagnosed with PAD from January 2015 to October 2019 at a tertiary center referral unit for photobiology was conducted to evaluate the demographic and clinical features of PAD.

A detailed standardized photoinvestigation was also performed, including analyses of monochromator phototesting responses to UVR and visible light (VIS), to assess wavelength sensitivity, erythemal thresholds, and responses to solar-simulated radiation in patients with a range of skin phototypes (SPTs).

“On the basis of clinical suspicion that patients with darker skin had differing characteristics from those with lighter skin, a subgroup analysis was performed for SPTs I to IV and SPTs V to VI. Subgroup comparisons used unpaired t tests or nonparametric equivalents as appropriate,” explained the study authors. “Multiple linear or logistic regression explored associations between demographic and clinical variables.”

A total of 869 patients underwent photoinvestigation, of whom 120 (14%) were diagnosed with PAD (median age, 45 years; IQR, 31-61 years; range, 5-83 years; SPTs I-VI; 58% female; 104 were adults [87%]).

All participants had a history of AD, and a majority of adult patients (60%) presented with sunlight-provoked or photodistributed eczema, with a median age at photosensitivity onset of 37 years (range, 1-72 years). Delays in diagnosis were common, with median age at diagnosis 8 years later than median age at photosensitivity onset.

Overall, 80 of 103 adults (78%) experienced very or extremely impaired QOL, with past-year Dermatology Life Quality Index (DLQI) scores greater than 10. Vitamin D (25-hydroxyvitamin D) insufficiency or deficiency (< 20 ng/mL) was also found among 82 of 119 (69%) patients.

“The multiple linear regression model evaluating associations between past-week DLQI score and other variables showed that provocation through window glass and age at photosensitivity onset were significantly associated with past-week DLQI score,” said researchers.

Findings further showed that broadband UV radiation provocation test results were positive for 112 patients (93%), narrowband phototest findings were abnormal for 23%, and photopatch test reactions were positive for 15%. Regarding those with abnormal monochromator phototest, sensitivity occurred to UV-A, UV-B, and/or visible light, and UV-A of 350 ± 10 nm was the most prevalent wavelength.

Compared with patients with lighter skin (SPT I to IV, n = 89), those with darker skin (SPTs V to VI, n = 31) were younger at photosensitivity onset (median age, 24 years [IQR, 15-37 years] vs 40 years [IQR, 25-55 years]; P = .003), were more likely to be female (23 [74%] vs 46 [52%]; P = .03), and had a lower vitamin D status and a higher frequency of abnormal monochromator phototest findings.

“The study’s findings suggest that improved knowledge of PAD presentation, demographic aspects, and photoinvestigation can assist patient diagnosis and treatment and that more attention should be given to this condition,” concluded the study authors.

Reference

Rutter KJ, Farrar MD, Marjanovic EJ, Rhodes LE. Clinicophotobiological characterization of photoaggravated atopic dermatitis. JAMA Dermatol. Published online July 27, 2022. doi:10.1001/jamadermatol.2022.2823