Prevalence and Trend of Photodermatoses in Thailand: A 16-year Retrospective Study at Siriraj Hospital.

Objective: Photodermatoses are a group of cutaneous disorders with abnormal reactions triggered by exposure to sunlight. Previous studies reported varying photodermatoses prevalence in Caucasians and African-Americans; however, it was seldom reported in the Asian population. The aim of our study was to determine the prevalence, clinical characteristics and trend of photodermatoses in Thailand. Materials and Methods: A retrospective chart review was performed at the Faculty of Medicine Siriraj Hospital, Mahidol University using diagnoses from the International Classification of Disease (ICD), Tenth Revisions codes, between January 2005 and September 2021. Results: A total of 561 patients with definite diagnoses of photodermatoses were identified. The prevalence of photodermatoses in the outpatient dermatology clinic was 3 cases per 1,000. The most common photodermatoses were chemical and drug-induced photosensitivity (39.4%), followed by immunologically-mediated photodermatoses (30.1%), photo-aggravated dermatoses (29.4%) and genophotodermatoses (1.1%). Overall phototesting was performed in 276 cases (49.2%). In our study, some photodermatoses had unique clinical characteristics including a pinpoint popular variant of polymorphous light eruption and adult-onset actinic prurigo. Over 16 years, the trend of patients being diagnosed with photodermatoses has continued to rise gradually with an increment of 1.67 times. Conclusion: Photodermatoses are uncommon in Thailand. Some photodermatoses have distinctive clinical features in Asian populations. The trend of photodermatoses in Thailand is continually rising, reflecting an increase in physicians' awareness and knowledge of these cutaneous conditions. [ABSTRACT FROM AUTHOR]