Photodermatitis from topical phenothiazines: A case series

Shedding a light on the importance of photopatch testing: A 12-year experience in a dermatology unit

BACKGROUND

Photopatch testing has been standardized for diagnosing photoallergic contact dermatitis but is still infrequently used.

OBJECTIVES

To characterize photopatch test (PPT) results and their clinical relevance.

METHODS

We collected retrospective data from patients photopatch tested in our Dermatology Unit (2010-2021), using the European PPT 'baseline' series, other allergens, and patient's own products, when appropriate.

RESULTS

Out of 223 patients, 75 patients (33.6%) were reactive with 124 positive PPT reactions, considered relevant in 56/223 patients (25.1%) and in 72/124 reactions (58.1%). Most reactions were caused by topical drugs (n = 33; 45.8%), such as ketoprofen or promethazine, and 7 (9.8%) by systemic drugs, such as hydrochlorothiazide and fenofibrate. 'Classical' ultraviolet filters were responsible for six positive PPT reactions whereas there was only three relevant PPT to the 'newer' UV filters. Patients' sunscreens/cosmetics or plant extracts caused 10 positive PPT each. Additional patch test reactions were observed, mostly to Tinosorb® M.

CONCLUSION

Contrary to the trend in ACD, most positive PPT reactions were caused by topical drugs, outweighing ultraviolet filters and cosmetics. We stress the low reactivity to the 'newer' UV filters included in the PPT series. PPT was occasionally positive in systemic drug photosensitivity, but overall PPT reactivity was low.

Photopatch testing in Chinese patients: A 5-year experience

BACKGROUND

In 2015, a Chinese expert consensus on photopatch testing (PPT) was established, based on European consensus methodology.

OBJECTIVES

To update current information on the prevalence of photoallergic contact dermatitis (PACD) to 20 photoallergens and their clinical relevance in the Chinese context.

METHODS

A retrospective analysis of 2372 patients who performed PPT in a tertiary referral center in China between 2015 and 2019 was completed. A total of 1208 PACD reactions were observed in 897 (37.8%) patients, and 413 reactions were of current or past relevance.

RESULTS

The proportion of reactions of current or past relevance was 34.2%. The most frequent photoallergens were chlorpromazine, thimerosal, potassium dichromate, and formaldehyde. The ultraviolet absorbers, benzophenone and Para-aminobenzoic acid, showed opposite gender distribution to PACD. Twenty-five patients (1.9%) developed PACD reactions to a newly added photoallergen preparation - fragrance mix I. Patients with chronic actinic dermatitis, widespread exposed-site or generalized dermatitis, and older age were more likely to have PACD.

CONCLUSIONS

This study is the first to profile PACD reactions with clinical relevance in China. The prevalence of PACD to culprit photoallergens was affected by regional peculiarities. Attention needs to be paid to the age, body-site distribution, and known diagnoses of patients for the identification of PACD.