This research project investigates the clinical and genetic associations of Actinic Prurigo (AP) in the Thai population. As a rare chronic photodermatosis, AP has been observed to occur more frequently in individuals with certain genetic predispositions, particularly specific Human Leukocyte Antigen (HLA) types. Previous studies have suggested variations in clinical presentation and HLA allele distributions between Asian and Western populations.

The primary aim is to explore the relationship between clinical manifestations of AP and genetic profiles, including HLA typing, among Thai individuals. Additionally, the study seeks to examine whether different HLA types are associated with varying responses to treatment.

The study design is a cross-sectional comparative study, involving both AP patients and age-matched healthy controls. Given the rarity of the condition, patient recruitment will be conducted across four collaborating institutions:

King Chulalongkorn Memorial Hospital Siriraj Hospital Institute of Dermatology

Inclusion Criteria:

• Thai ethnicity
• Diagnosed with Actinic Prurigo (AP) according to the diagnostic criteria defined for this study
• Mentally competent, able to communicate, and able to read Thai.
• Participants receiving Thalidomide treatment must use two simultaneous methods of contraception, starting at least 4 weeks prior to initiating the medication and continuing throughout the treatment period and for at least 4 weeks after discontinuation.

Exclusion Criteria:

• History and physical examination findings suggestive of other photodermatoses such as Lupus erythematosus, Porphyria, or Polymorphous Light Eruption, among others.
• Elevated Epstein-Barr Virus (EBV) viral load detected in blood testing (EBV viral load will be tested in all participants).
• Low Minimal Erythema Dose (MED) to UVB radiation as the only abnormal finding.

Actinic Prurigo (AP)